Democratic Incumbent Resilience in the Post-1980 Senate:
A Theory of Partisan Issue Competence
Nicholas Goedert
Postdoctoral Fellow
Department of Political Science
Washington University in St. Louis
April 2013
Prepared for 2013 Midwest Political Science Association Conference
I. Introduction
Elections to the United States Senate have been subject to far less study than either presidential
elections or elections to House of Representatives. Moreover, many of these studies have focused on
one particular aspect of Senate elections: why they appear to be much more competitive than
congressional races. Until recent decades, this question may have been the most obviously relevant:
between 1948 and 1980, reelection rates for Senators fell below two-thirds in four separate years,
while hovering around 90-95% for House races for the entire period. Scholars have broached a
variety of theories for the difference, none of which include party as part of larger story.
But more recent trends in Senate elections have demanded a new explanation. Following the
“Reagan revolution” that swept Republicans into office in 1980, Senators have been re-elected at a rate
of 88%. But more importantly, Democrats have much more resilient to reelection challenges than
Republicans, winning 93% of the time, a figure comparable with the success of Congressional
incumbents of both parties. While “change” elections in the past have frequently featured the defeat of
7 to 10 Senators of on party, even the most successful Republican years in the past three decades (1994
and 2010) each saw only two incumbent Democrats fall. And while Republican incumbents have had
much less success in winning reelection, losing 18% of the time, their party has been almost
symmetrically successful in winning 58% of open Senate contests regardless of the party of the retiring
incumbent.
Given these apparent disparities between the parties, is seems prudent to include party as
possibly a crucial independent variable in the analysis of recent Senate elections, and to try to
determine what sort of underlying behavior, either from voters or elite actors, may be generating these
disparities. This paper will advance one explanation: that Democratic incumbents have been more
successful at running for reelection because voters perceive them as more proficient in attaining statespecific benefits than Republicans, and thus voters place more value on incumbency and seniority
when evaluating a Democratic candidate then when evaluating a Republican. The paper will explore
1
this theory through analysis of Senate election data from 1984 through 2012, and survey results from
the 1988-1992 NES Senate Study and 2008-2010 Cooperative Congressional Election Survey.
II. Background
Campaign Intensity in Senate Elections
For the past several decades, much of the study of Senate elections has focused on explaining
why they are more competitive than House elections. Although the specific conclusions of this
research vary, much of it centers around arguments about challenger quality and campaign intensity.
Beyond the studies of divided government mentioned in the next section, virtually none of this
research explains, addresses, or even notices systematic difference in electoral performance between
the parties. For example, policy position is also shown to be important in the outcome of
congressional elections (Wright and Berkman 1986), with incumbents expecting tough challengers
more likely to adopt moderate positions (Burden 2004). But the analysis of candidates and voters of
both parties is consistently seen as completely symmetric in this research.
Some have argued that incumbent vulnerability is related to constituency size (Hibbing and
Brandes 1983, Abramowitz 1988), with incumbents in larger states more likely to be defeated because
they are less personally in-touch with a large number of their constituents. This would lead to the
natural conclusion that Senators will be more vulnerable than members of Congress in all but the
smallest states. But this is far from a universal finding: some authors have found very little
relationship between constituency size and competitiveness in Senate elections (Krasno 1994, Westlye
1991), while others have argued that small constituencies may lead to more competitive elections
through higher quality challengers (Lascher 2005).
Westlye (1991) argues that Senate campaigns can be divided into categories of intensity: “low
key” and “hard fought”, largely based on the viability of the challenger. When the campaign fails to
attract a high quality challenger, the dynamics of the Senate campaigns resemble those of a typical
2
House campaign, and incumbents are almost always reelected. But in the case of high-intensity
campaigns, with quality challengers, high media visibility, and high campaign spending, incumbents
become very vulnerable, more resembling to a national campaign. Krasno (1994) similarly concludes
that “Senators lose more often because they are more likely to face formidable challengers who wage
intense campaigns.” Some studies argue that high intensity campaigns trigger different decision
processes in the mind of voters, with partisanship and ideology playing a greater role in hard-fought
races (Kahn and Kenney 1997).
The concept of campaign “intensity” meshes well with common findings that Senate election
outcomes are much more sensitive to challenger campaign spending than incumbent spending
(Jacobsen 1980, Abramowitz 1988). While incumbent spending is less variable, high challenger
spending may be a signal of a high intensity campaign, and low challenger spending a signal of a “low
key” race. Even having a substantial “war chest” prior to any candidate entry has been found to do
little to deter high profile challengers in Senate elections (Goodliffe 2007). Indeed, Jacobson (2000)
finds that high levels of challenger spending tend to induce higher levels of incumbent spending,
probably indicative of high campaign intensity. I believe it is thus reasonable to used combined
campaign spending, relative to constituency size, as a measure of challenger viability and campaign
intensity.
Jacobson’s Political Explanation for Divided Government
Although the theories surveyed above go a long way toward explaining why some incumbents
are more vulnerable than others, they can do little to account for systematic differences in party
performance. But another area of study, divided government, does provide possible insights. During
the 1980’s, political scientists noticed that the post-war American government was most often
characterized by Republican control of the executive branch and Democratic control of the legislature.
Some scholars broached an institutional explanation for this trend, while other sought to explain it in
3
terms of voter behavior. Fiorina (1988) advanced a behavioral explanation that does not depend on
inherent differences between the parties: voters do not completely trust either party, and thus
deliberately vote for divided government so that institutional barriers will prevent the enactment of
either party’s least desirable policies or schemes. In contrast, Jacobson (1990) argues that voters do
intentionally vote for divided government, but their choice of which party to put in control of which
branch is also deliberate and actually based on perceived differences between the parties.
Jacobson notes that in recent decades, Republicans have been judged more competent in
dealing with issues that affect the nation as a whole, such a defense, taxation, and inflation, while
Democrats are judged more competent on issues that affect small groups and localities, such as
unemployment, agriculture, education, aid for the poor, and problems affecting minorities. He also
notes that voters prefer Presidents who will focus on national problems, but congressional
representatives who will put the interests of their district ahead of the national interest. Therefore,
there is natural fit between preferring to have a Republican as your president and a Democrat as your
congressman. Essentially, voters want a Republican president to bake the pie, and a Democrat in
Congress to make sure they get the biggest slice.
This explanation relying on specific party issue competence has perhaps lost some luster in the
wake of the Republican revolution of 1994 (when voters elected a divided government in the opposite
configuration to that suggested by Jacobson). Jacobson (in Galderisi 1996) argued that Republicans in
Congress successfully “nationalized the election” to an extent not seen in decades to overcome their
disadvantage on local issues. But regardless of the specific results of any election, if we do see that
parties are perceived as being divergently competent on national and district-specific issue, we may see
not only differences in the extent to which voters see the parties as appropriate to control each branch
of government. We may also see differences in the way voters value candidate traits like seniority and
ideological congruence within a single branch of government. This difference forms the basis for the
4
partisan issue competence explanation for the disparities observed in Senate elections. Part III details
these disparities, while Part V details the hypothesis.
III. Demonstration of Partisan Disparity
This paper explores the divergent success of the two parties in Senate elections using recent
election data, supplemented by NES Senate Study and CCES survey responses. The data set I employ
consists of the results of all Senate elections held on a national general election day from 1984 to
2012.1 The data set is 511 data points, which amounts to five elections for each seat plus a handful of
special elections.2
This period can be characterized by a high level of parity between the parties. The largest postelection number of seats controlled by either party during this time is 59; the Democrats held majority
control of the Senate during 8 of the 15 elections (1988-1994, 2002, 2008-2012), and the Republicans
controlled it during the other 7. This is in stark contrast to the 1961-1980 period, during which the
Democrats had consistent control with majorities in the 57-67 seat range.
The sample consists of 256 seats held by Democrats (including Independents caucusing with
Democrats), and 258 seats held by Republicans. 267 races were won by Democrats, and 247 were won
by Republicans. The distribution is of open and incumbent seats and the percentage of pick-ups in
each category are shown in Table 1 and Figure 1 below.
1
1984 was chosen as the first year in the data set to balance the number of times each seat was
counted. As noted in the next section, both the first and last year of the data set constitute two of three
exceptions to the general pattern found in the paper, so choosing different start or end dates would
strengthen this result.
2
Race where an incumbent in defeated in a primary are counted as open seats; two races were
excluded where an incumbent was defeated in a primary but won reelection as an independent.
5
Table 1. Senate Turnover by Party, 1984-2012
Won by
Democrat Republican
Total
Democratic Incumbent
185
13
197
Republican Incumbent
36
170
206
Democratic Open Seat
32
26
59
Republican Open Seat
14
38
52
Turnover %
6.6%
17.5%
44.1%
26.9%
Figure 1. Senate Seat Turnover Percentage, Incumbents vs. Open Seats, 1984-2012
Note the sharp disparity between Turnover % among Democratic Incumbents and Republican
Incumbents, and an inverse disparity between Democrat-held Open Seats and Republican-held Open
Seats. During the past 30 years, Democrats have made most of their gains in the Senate by defeating
incumbent Republicans, while Republicans have made most of their gains by winning open seats.
We can regress the probability of pick-up by the opposing party against the incumbent party
holding the seat using a probit analysis as shown in Table 2. Without controlling for any other
variable, an incumbent is significantly more likely to lose if he or she is a Republican, while the open
seats are significantly more likely to change parties if the retiring incumbent is a Democrat.
6
Additionally, we can do a regression analysis on the percentage of the vote received by the incumbent
party against the party indicator, also shown in Table 2.3 Although Republican incumbents, both
winners and losers, receive a slightly smaller fraction of the vote compared with incumbent Democrats,
and Republicans overperform Democrats by a similar margin in open seats, neither difference is
statistically significance.
There appears to be some evidence that Republican incumbents in the post-1980 period have
performed consistently worse than Democrats, while Republicans have performed consistently better
in open seats, evidence that will only be strengthened as we consider additional factors. Part IV of this
paper will address a few possible simple explanations for this phenomenon, while Parts V through VIII
will advance a more a more subtle explanation: that voters value incumbency more in Democrats
because they believe Democrats are more competent on issues where incumbency and seniority are
valuable.
Table 2. Effect of Party on Senate Election Results, 1984-2012
Likelihood of Turnover
(Probit)
Incumbents
Open Seats
Republican
0.57***
-0.53**
(0.17)
(0.25)
Constant
-1.51
-0.13
(0.14)
(0.17)
Incumbent Party Vote
(OLS)
Republican
Constant
-1.09
(0.90)
60.85
(0.64)
2.30
(1.66)
49.38
(1.14)
n
402
109
Notes: Standard errors in parentheses. *p<.10, **p<.05, ***p<.01
3
The incumbent party vote share measure is adjusted in Table 2 to account for unopposed races as
described in Part VII.
7
IV. Trivial Hypotheses
In this section we will show that the disparity in electoral success resists an obvious
explanation, persisting throughout many subcategories of the data. In most cases, merely visualizing
the data can dismiss these explanations. In all the graphs in this Part, I have indicated Democrat-held
seats in blue and Republican-held seats in red; open seats are in a lighter shade than incumbent seats.
Note that the light blue line is almost always above the light red line, while the dark blue line is almost
always below the dark red line.
Analysis by Year and Cycle
One possible hypothesis is that the disparity is due to just two or three fluky election years. For
example, if there were only one or two particularly pro-Republican year in which a huge number of
Democrats retired, and/or one or two very pro-Democratic years with very few retirements, a theory
about persistent trends throughout the era would be less plausible. But this does not appear to be the
case.
I have divided the data into 6-year cycles, with each seat is up for election once in each cycle.
Figure 2 shows the turnover percentage in each cycle; with one exception, the Republicans lost more
incumbents than open seats in every cycle, while the Democrats lost more open seats than incumbents
in every cycle.
8
Figure 2. Senate Seat Turnover Percentage by Cycle, 1984-2012
Additionally, the disparity holds regardless of whether the election year was overall favorable
to the Democrats, favorable to the Republicans, or balanced. The data set contains five elections that
tilted favorably to the Democrats, four that favored the Republicans, and six that were essentially
neutral. In years when the Democrats picked-up seats, they did so primarily be defeating Republican
incumbents; when the Republicans gained seats, they did so by winning a large number of seats from
retiring Democratic incumbents. In most neutral years, the Republicans won most of the open seats,
but lost more incumbents than the Democrats; only three elections out of 15 were slight exceptions.
Democratic wave elections:
1986: Democrats won 3 of 5 open seats, defeated 7 incumbents, lost 0 incumbents
2000: Democrats won 4 of 5 open seats, defeated 5 incumbents, lost 1 incumbent
2006: Democrats won 2 of 3 open seats, defeated 6 incumbents, lost 0 incumbents
2008: Democrats won 3 of 5 open seats, defeated 5 incumbents, lost 0 incumbents
Republican wave elections:
1994: Republicans won 9 of 9 open seats, defeated 2 incumbents, lost 0 incumbents
2002: Republicans won 6 of 7 open seats, defeated 2 incumbents, lost 1 incumbent
2004: Republicans won 6 of 8 open seats, defeated 1 incumbent, lost 0 incumbents
2010: Republicans won 10 of 14 open seats, defeated 2 incumbents, lost 0 incumbents
9
Neutral elections:
1988: Republicans won 4 of 6 open seats, defeated 1 incumbent, lost 3 incumbents
1990: Republicans won 3 of 3 open seats, defeated 0 incumbents, lost 1 incumbent
1996: Republicans won 9 of 14 open seats, defeated 0 incumbents, lost 1 incumbent
1998: Republicans won 3 of 5 open seats, defeated 1 incumbent, lost 2 incumbents
Exceptions:
1984: Republicans won 1 of 4 open seats, defeated 1 incumbent, lost 2 incumbents
1992: Republicans won 3 of 9 open seats (no turnover), defeated 2 incumbents, lost 2 incumbents
2012: Republicans won 3 of 11 open seats, defeated 0 incumbents, lost 1 incumbent
Analysis by Region
Another possible explanation is that the disparity is due to regional partisan shifts in the
country during this period, combined with the timing of retirements. For example, one could posit
that many Senate seats in conservative Southern states were only able to remain Democratic as long as
senior incumbents from an earlier era held the seat, but when those incumbents retired, many Southern
seats immediately shifted to the Republicans (Black 2003).
As a quick test of regional theories, I divided the states into four regions, each with 12 or 13
states. The South consists of the former Confederate states plus Oklahoma. Unsurprising, Democrats
perform best in the East and worst in the South; the Midwest shows the highest degree of turnover
overall. But the trends within each party still hold for each region, shown in Figure 3. It is even true
that more incumbent Southern Republicans were defeated during this time than incumbent Southern
Democrats (although the percentage of Democrats defeated is slightly higher).
10
Figure 3. Senate Seat Turnover Percentage by Region, 1984-2012
Analysis by Seniority:
To address another possible explanation, if the GOP was winning a disproportionate number of
open seats in a certain cycle, that may create a disproportionate number of weak GOP freshmen
running for reelection six years later. But as shown in Figure 4 below, although freshmen lose slightly
more often than average, Republican Senators running for a third or fouth term lose more often than
those running for a second. So it does not seem that weak freshmen can fully account for the disparity.
While Senators from both parties running for a fourth terms or more almost never lose, notice
that open seats also rarely flip when a 4+ term Senator is retiring. It could be that there is a common
cause here, and that 4+ terms is more signal of a ideologically unbalanced state than any actual value
of seniority.
11
Figure 4. Senate Seat Turnover Percentage by Seniority, 1984-2012
Constituency Size
Any claim that the observed partisan difference can be explained by constituency size is
probably implausible for two reasons. First, as noted in the Part II, Krasno conducts this analysis and
concludes there is no evidence for a relationship between constituents size and incumbent performance
in all but a handful of very large states. Second, if the effect is in the direction posited by past
research, this would probably predict a partisan effect in the reverse direction from what we observe:
incumbents would be safer in small states, which tend to be more heavily Republican, and more
vulnerable in large states, which are more heavily Democratic, and thus on average we would expect to
see more vulnerable Democratic incumbents.
Nevertheless, I ran both the probit and linear regression analyses from Table 1 including a
variable indicating the number of congressional districts in the state. As this variable is also correlated
with a state’s partisan balance, I have also included the “State Partisanship” variable, detailed in Part
VII. The results of this analysis are shown in Table 2 below.
12
Table 2: Senate Seats 1984-2006
Including Congressional Districts and Partisan Advantage
Republican
CDs
State Partisanship
Constant
Incumbents
Open
(1)
(2)
(3)
(4)
Turnover Incumbent % Turnover Incumbent %
(Probit)
(OLS)
(Probit)
(OLS)
0.82***
-3.25***
-0.026
-1.12
(0.19)
(0.85)
(0.29)
(1.56)
0.0091
-0.21***
0.019
-0.15*
(0.0090)
(0.042)
(0.016)
(0.087)
-0.033***
0.24***
-0.062***
0.33***
(0.0072)
(0.031)
(0.013)
(0.058)
-1.63***
62.4***
-0.39
50.9***
(0.17)
(0.72)
(0.24)
(1.28)
Observations
402
402
109
R-squared
0.183
Standard errors in parentheses; *** p<0.01, ** p<0.05, * p<0.1
109
0.265
Controlling for state partisanship, the number of congressional districts in a state has no effect on the
likelihood of a partisan flip in the case of incumbent or open seats. Larger constituencies do have a
significant effect on incumbent vote percentage, but the gap between Republicans and Democrats
persists and is statistically significant. So the disparity between the parties’ electoral success cannot be
merely attributable to constituency size.
Campaign Spending & Campaign Intensity
Campaign spending and intensity will play a role in the issue competence theory described
below. The explanation I wish to refute in this section is simply that Republican incumbents and
challengers to incumbents do poorly because they have lower relative campaign spending. This claim
is clearly false. Relative to Democrats, Republican spend more in incumbent races and open seats
races. Based on data from FEC filings, the median spending ratio in favor of the incumbent was 3.3to-1 in the case of Republican incumbents, and 2.9-to-1 in the case of Democratic incumbents.
Republicans did outspend Democrats by 1.2-to-1 in the median open seat election, so this could
13
possibly be a factor in their relative open seat success. But since the modest spending gap in favor of
Republicans is also present in the incumbent races, it cannot explain their failure in incumbent races.
Median spending intensity was also slightly higher in cases when Democratic incumbents were
running than Republican incumbents (11.8 vs. 11.5).
Measuring campaign intensity by total spending, as detailed on Part VII, also reveals that seats
with Democratic incumbents had slightly greater average spending intensity, so it is also not true that
Democratic incumbents drew consistently less financially viable opponents.
V. The Partisan Issue Competence Hypothesis
Having dismissed trivial explanations, this paper posits that the difference in electoral
performance between the parties is explained by voters’ differing assessments of the parties’
competence on issues where incumbency and seniority is valued (specifically, acquiring state-specific
benefit like pork projects). The “issue competence” hypothesis can be stated as follows: voters see the
Democratic party as more proficient in attaining state or district-specific benefits (“distributional”
issues), while seeing the Republican party as more proficient in addressing “ideological” issues.
In order for the asymmetric issue competence hypothesis to actually translate into divergent
success for Democratic and Republican Senate incumbents, three steps must be true:
1.) Voters must perceive Republican senators as being stronger on ideological issues, and/or
Democratic senators as being stronger on local or “distributional” issues
2.) At the individual level, voters must weigh ideological similarity more heavily when
considering a vote for a Republican incumbent, and seniority or experience (representing
likelihood of success on local/distributional issues) more heavily when considering a vote for a
Democrat.
14
3.) At the aggregative level, this asymmetry must result in ideology having greater effect on the
electoral success of Republicans, and seniority having greater effect on the electoral success of
Democrats.
This paper will attempt to address step (1) through evidence from the ANES Senate Study, step (2)
through results from the 2008-2010 CCES, and step (3) by an analysis of the past 30 years of Senate
election results. To preview the results in the next three sections, I find strong support in the data for
steps (1) and (3), but no support for step (2). So in order for the for partisan issue competence to be
convincingly shown to affect Senate elections, there is still at least one missing link that must be
addressed by future research.
This is primarily a hypothesis about the behavior of voters, and not the strategic interactions of
candidates and other elite actors. Thus, while we want to control for factor such as challenger entry
and fundraising, these are not our variables of interest. The causality of these variables admittedly
may run in both directions (high quality challengers will tend to enter against incumbents inclined to
perform badly, and incumbents will perform worse if a high-quality challenger), and this is a
complication for any model including such variables. For our purposes, we will bracket this
complication and focus on the variables of direct interest to or hypothesis.
Additionally, the fact that this is a voter behavior explanation has an important impact of our
choice of dependent variable. We are mostly interested in how many voters voted for a candidate, and
not which candidate won. Thus, our independent variable is the incumbent party’s percentage of the
vote, and not whether the party won. The winner might be an important variable were we investigating
a hypothesis of elite strategy, where getting past the winning threshold is the ultimate goal. But for our
purpose, we will consider a shift from 55% of the vote to 60% of the vote just a meaningful as a shift
from 47% to 52%.
However, if we look purely at voter percentage, we encounter a problem in that in some races,
a candidate runs unopposed or with only token opposition, which will distort vote percentages even
15
controlling for other variables. In some case, a strong incumbent may be running without meaningful
opposition, but his or her share of the vote may be hugely affected by whether another sure-loser
candidate bothers to get his name on the ballot. We are mostly concerned with voter behavior in
elections that are actually contested, but we do not want to entirely dismiss uncontested elections, as
they are likely uncontested because the potential candidates have made a certain assessment about the
likely behavior of voters.
Another way to look at this is that we wish to finely assess voter behavior in high-intensity
races, while lumping very low-intensity races together (although my definition of low-intensity races is
more narrow that Westlye’s). The solution I have used is to create an “Incumbent Percent Adjusted”
variable, which is equal to the incumbent party’s actual percentage of the vote if that percentage is
between 25% and 67%. If the percentage is above 75%, Incumbent Percent Adjusted is set equal to
75%, and it is set to 25% if the actual percentage is less than 25% (but no incumbent in the data
received less than 25%).
Approximately 10% of the sample lies in these extreme ranges. Note that
running all of the analyses on actual incumbent party performance yields substantive results that are
almost identical, but this is problematic in that it does nothing to adjust for unopposed candidates.
VI. Evidence on Issues Perceptions (NES Senate Study Data)
To test the partisan issue competence theory, we first want to establish that voters view the
parties different, and specifically, that they view Democratic senators as more proficient in securing
district-specific benefits. We might express these hypotheses as follows:
1.) Voters who value the ability of a Senator to attain state-specific benefits more than his or
her positions on nation issues will tend to vote more frequently for Democratic Senate
candidates than voters who value a candidate’s national issue positions more;
2.) Voters will more frequently identify the ability to attain state-specific benefits as a positive
trait of Democratic incumbent than of Republican incumbents;
16
The data set used here is the NES Senate Election study, which was a panel study run during the 1988,
1990, and 1992 elections. The Senate study asked a wide array of questions about senators, members
of Congress, and congressional election challengers, and samples approximately evenly across all
states. About 70 respondents were surveyed in each state in each general election year, yielding a total
sample of about 9000. However not all questions were asked in every year; for example, the question
about which activity of a U.S. Senator is most important (used in the first analysis below) was asked
only in 1990.
Although this survey does provide us some evidence about voter attitudes toward the parties, it
is unfortunately that it cannot be more usefully connected with out data set of election results, as the
survey was only run from 1988-1992. While this constitutes a full cycle of Senate elections, these
years were actually somewhat anomalous in the post-Reagan era in that they constitute an period of
high partisan stability and low turnover in Senate elections, in contrast to both the immediately
preceding and succeeding elections (1986 and 1994) and the first several general elections in the 21st
century. It was also a period of constant Democratic control of the Senate, in contrast to the
Republican control of the preceding and succeeding periods. Thus, it is probably not a data set that
will, by itself, explain the electoral trends of the post-1980 era, as many of these trends were noticeably
absent during the particular years of the Senate Study.
The Senate study includes the following question which asks respondents to balance statespecific benefits against national issues:
(PS087) Which of the following three activities you think is most important:
-
helping people in the state who have personal problems with the government;
-
working in Congress on bills concerning national issues; or
-
making sure the state gets its fair share of government money and projects?
17
Under the partisan issue competence theory, we would expect respondents who believe that making
sure the state gets is fair share of government money and projects would vote for a Democratic Senate
candidate more frequently than those who believe working on bills concerning national issues would.4
Table 3 below shows the vote choice among Senate voters broken down by response to this
question.
Table 3. Vote Choice by Most Important Senate Activity
% of Sample
Senate Vote
Democrat
Republican
Whole
Sample
100%
51%
(745/1462)
49%
(717/1462)
Most Important Part of Senator's Job
Personal
National
State's Share of
Problems
Issues
Money & Projects
15%
48%
24%
51%
(111/218)
49%
(107/218)
49%
(347/708)
51%
(361/708)
54%*
(270/501)
46%
(231/501)
Difference b/w parties on National Issues vs. State Share significant at p<.10 (chi^2 test)
As shown in the table, 49% of voters whose believe the most important activity for Senators
was working on national issues voted for the Democratic senate candidate, while 54% of voters who
believe state-specific benefits are the most important activity voted for the Democrat, a difference
significant at the 90% level. So while the difference is not huge, there does appear to be some
evidence that voters who value state-specific benefits tend to vote more frequently for Democrats in
Senate elections.
As an even more direct test of the partisan issue competence theory, we can ask whether voters
positively associate the acquisition of state-specific benefits more frequently with Democratic senators
than with Republican senators. The Senate Study asks respondents if there was anything they
4
This theory does not offer a prediction with regard to voters who believe helping people with
personal problems is most important. Also note that, for each of these options, the Senate Study asks
respondents whether they think the activity is “very important”, “somewhat important”, etc. However,
the overwhelming majority of respondents answer “very important” to both the “state share” question
and the “national issues” question, making this a less useful measure of voters’ priorities.
18
“particularly liked” about each of their senators and Senate candidates, and recorded open-ended
responses. I examined what fraction of respondents, among those who could name at least on thing
they liked, listed at least one trait associated with a state or district-specific benefit for each incumbent
Senator not running for reelection, each incumbent running for reelection, and each Senate election
challenger. The response codes that were coded as state-specific benefits were:
1.) Has helped local (district) economy; brought money, projects, jobs to district
2.) Watches out for the interests of the district or region
3.) Favors agriculture subsidies/price supports/help for farmers
4.) Favors specific government jobs programs
5.) Support for specific industry
6.) Support for infrastructure programs5
The percentage of each candidate class that received favorable state-specific mentions are shown in
Table 4 below.
Table 4. % Listing State-Specific Benefits As "Likes" of Senator or Candidate
Among those who could list at least one "Like"
Party of
Senator/Candidate
Democrat
Republican
Incumbent Senator not
currently in campaign
18%
(745/4207)
16%
(531/3272)
Incumbent running
for reelection
19%***
(282/1425)
14%
(176/1220)
Non-Incumbent
Senate Challenger
5%
(32/686)
4%
(25/639)
***Difference between parties among incumbents running for re-election significant at p<.01.
Among senators not currently up for election, Democrats attract a slightly higher, but
nonsignificant, rate of state-specific benefit mentions (18% versus 16% of Republicans).
Unsurprisingly, non-incumbent challengers of both parties receive such mentions very infrequently.
However, among Senators currently involved in reelection campaigns, Democrats attract a state-
5
More than 60% of the qualifying responses were under code (2); most of the remainder were split
between (1) and (3), with (4), (5), and (6) receiving a negligible number of responses.
19
specific benefit mentions at a substantially higher rate (19% versus 14% for Republicans). The
difference between the parties among incumbents up for reelection is statistically significant at the
99% level.6
So it appears there is some support for hypothesis (2), even if it only manifests itself during
actual Senate election campaigns. This could be because Democratic senators make a conscious effort
to prime this, either through their campaign or their actual job performance, or it could simply be that
voters are more likely to think about party differences during a campaign; at this point, I am agnostic
between theses theories. It is also possible that Democratic control of the Senate during the years of
this survey accounts for the difference; it would probably be worthwhile to look for additional
evidence during times of Republican control in future research.
VII. Evidence from Aggregated Vote (Senate Election Data)
Another step in the analysis is to test whether perceived differences in issue competence affect
aggregate election results. As above, the data set for all of these analyses is 30 years worth of Senate
elections nationwide (excluding a handful on special elections not held on a regular general election
date), and the dependent variable is always the adjusted percentage of the vote received by the
incumbent party. To measure ideological congruence, I include measures of the partisan balance of the
state, and the incumbent’s ideological extremism. To measure experience, I include the incumbent’s
number of terms in office.
Definition of Variables
•
State Partisanship: I have included in the analysis a measure of state partisanship based on
presidential election results. This measure, State GOP Advantage, is a measure of how much
6
The substantive result of this table are unchanged if one instead evaluated the percentage of all
respondents asked to name a “like”, rather than the percentage among those who could name at least
one like; there is essentially no difference by party in the fraction of respondents able to volunteer a
“like”.
20
more Republican the state is than the national average, based on the two most recent
presidential elections. So for a 1990 Senate race in Colorado, State GOP Advantage = ((Bush
1988 % in CO – Dukakis 1988 % in CO) – (Bush 1988 National % - Dukakis 1988 National
%)) + ((Reagan 1984 % in CO – Mondale 1984 % in CO) – (Reagan 1984 National % Mondale 1984 National %)) / 2. If the state is less Republican than the national average, this is
negative. The variable used in my regressions, State Partisanship is the State GOP Advantage
when the incumbent is a Republican, and the inverse of this when the incumbent is a Democrat.
•
Candidate Extremism: Canes-Wrone et al. (2002) suggests that more extreme members of
Congress gain less electoral support. My measure of extremism is the absolute value of an
incumbent’s DW-NOMINATE score in the term immediately prior to the election year. It thus
ranges from 0 to 1, with lower values indicating moderation.
•
Seniority: My hypothesis suggests that Democratic incumbents will be better able to capitalize
electorally on their proficiency in attaining state-specific benefits. One easily-measured factor
that enhances this ability is seniority (the number of terms the incumbent has been in office),
which helps the incumbent get on powerful committees, committees appropriate for his or her
particular state’s interests, appropriate subcommittee chairmanships, and other leadership roles.
The variable used in regressions, Terms is the number of complete Senate terms that the
incumbent had served prior to the election. For open seats, it the number of terms serves by the
retiring Senator.
•
Campaign Spending: I am including two variables for campaign spending. One is a measure of
the incumbent party’s spending advantage (or disadvantage) over the challenging party, while
the other is a measure of total spending in the campaign, functioning as a control for theories of
challenger spending and campaign intensity. The first variable, Incumbent Spending
Advantage, is the logged ratio of incumbent party spending to challenger party spending (with a
21
small constant added to each spending figure to avoid problems with unopposed and inactive
campaigns). The result is a variable with a range of approximately -4 to 4, with 0 representing
equal spending by both parties, and a 4 representing the incumbent party outspending the
challenger party approximately 50-to-1.
•
The second variable, Spending Intensity, is a measure of the total level of spending in the
campaign relative to the size of the state. It is calculated as follows:
SI = ln(
GOP Spending + c
Dem Spending + c
) + ln(
) , where c is a small constant as described
1000 • CDs
1000 • CDs
above, and CDs is the number of congressional districts in the state. The result is a variable
that is approximately normally distributed with a mean of 11.5 and a standard deviation of 2.5.
Comparing Open and Incumbent Seats
We will first analyze how these variables affect incumbent electoral performance on the whole
data set, both including and excluding a indicator for the party of the incumbent. If the partisan effect
disappears when we include one or more of these variables, it is likely the partisan differences
motivating this study are mainly a coincidental result of collinearity with one of these relevant, but
already studied, effects. Table 5 shows these regression results.
22
Table 5. Effect of Ideology and Seniority on Senate Election Results, 1984-2012
Incumbent Vote %
Republican
State Partisanship
Candidate Extremism
Terms in Office
Inc. Spending Adv.
Spending Intensity
Constant
Incumbent
(1)
Open Seat
(2)
Incumbent
(3)
Open Seat
(4)
-
-
0.12***
(0.029)
-6.11***
(2.24)
0.76***
(0.22)
2.41***
(0.38)
-1.21***
(0.15)
70.9***
(2.14)
0.20***
(0.053)
-0.77
(3.62)
-0.40
(0.38)
4.93***
(0.65)
1.18***
(0.35)
35.5***
(4.56)
-2.99***
(0.66)
0.17***
(0.030)
-8.33***
(2.24)
0.59***
(0.22)
2.51***
(0.37)
-1.17***
(0.15)
72.7***
(2.12)
-1.43
(1.28)
0.21***
(0.055)
-0.78
(3.62)
-0.41
(0.38)
5.00***
(0.65)
1.12***
(0.36)
37.0***
(4.72)
Observations
402
109
402
R-squared
0.512
0.534
0.537
Standard errors in parentheses; *** p<0.01, ** p<0.05, * p<0.1
109
0.540
We immediately notice two major facts in Table 5. First, in the regression excluding the party
indicator, all of the variables mentioned above have significant effects in the expected direction.
Partisan advantage, seniority, spending advantage, and a low intensity campaign all substantially
improve an incumbent’s performance. In the case of open seats, state partisanship advantage and
spending disparities have an even greater effect on the incumbent party’s performance than they did in
the incumbent case, while ideology and seniority of the retiring incumbent unsurprisingly have no
significant effect.
Second, the inclusion of the party indicator reveals that Republican incumbents still
significantly underperform Democrats even when controlling for state partisanship, seniority, and
spending. Moreover, the inclusion of incumbent party does not substantially impact the effect of any
of the other variables. So it seems that, as in Part IV, there is no obvious collinearity explanation for
the divergent success of incumbents of the two parties.
23
Comparing Democratic and Republican Incumbents
For the asymmetric issue competence hypothesis to explain the greater success of Democratic
incumbents, we would expect to find the following effects in the aggregate data:
1.) State Partisanship would have a greater effect on vote for Republican incumbents than
Democratic incumbent
2.) Candidate Extremism would have greater effect on vote for Republican incumbents
3.) Seniority would have greater effect on vote for Democratic incumbents
Table 6 provides support for each of these assertions. The first column of this table replicated
column 1 of Table 5 (seats with incumbents running only), while the second column includes the same
variable, but adds interactions with incumbent party. We see significant effects in the expected
direction in all cases: the effect of State Partisanship*GOP and Candidate Extremism*GOP are
positive, while the effect of Terms*GOP is negative. It does appear that ideology has a greater effect
on the electoral fortunes of Republican incumbents, and seniority a greater effect on Democratic
incumbents.
24
Table 6. Effect of Interacted Party and Ideology/Seniority on Election Results
(Incumbent Senators only, 1984-2012)
Nationwide
Post-1994
Non-South
South
(5)
Incumbent Vote %
(1)
(2)
(3)
(4)
State Partisanship
State Partisanship*GOP
Candidate Extremism
Candidate Extremism*GOP
Terms in Office
Terms in Office*GOP
Inc. Spending Adv.
Spending Intensity
Constant
0.12***
(.03)
-6.11***
(2.24)
0.76***
(0.22)
2.41***
(0.38)
-1.21***
(0.15)
70.9***
(2.14)
0.11***
(0.041)
0.10*
(0.053)
-4.90*
(2.81)
-5.54**
(2.59)
0.88***
(0.27)
-0.61*
(0.37)
2.43***
(0.38)
-1.21***
(0.15)
71.4***
(2.10)
402
402
Observations
.512
0.539
R-squared
Standard errors in parentheses; *** p<0.01, ** p<0.05, * p<0.1
0.063
(0.044)
0.14**
(0.057)
-3.31
(3.08)
-3.57
(2.93)
0.81***
(0.28)
-0.71*
(0.41)
3.15***
(0.44)
-1.08***
(0.17)
69.0***
(2.55)
0.16
(0.14)
-0.12
(0.17)
-12.0
(8.54)
6.25
(7.96)
1.30
(0.90)
-1.38
(1.00)
-0.48
(0.75)
-2.52***
(0.33)
87.8***
(4.17)
0.09*
(0.05)
0.10*
(0.06)
-3.91
(3.51)
-4.29
(2.97)
1.00***
(0.31)
-0.78
(0.42)*
2.57***
(-0.50)
-0.99***
(0.20)
68.0***
(3.26)
307
0.560
95
0.638
233
0.585
Columns 3 and 4 of Table 6 break out the southern states from the rest of the country. The
observed interacted effects of party and ideology/seniority are not present in Southern states;
particularly with respect to ideology, not only is the effect of the interacted variables not significant, its
sign is in the opposite direction; if anything, ideology has a greater effect on Southern Democrats than
Southern Republicans, although the limited sample here yields very high standard errors. Recall that
this is the only region of the country where Republicans are not defeated at a higher rate than
Democrats, and thus we might not expect the issue competence hypothesis to work the same way in
this region. The final column shows that these effects hold if we confine the results to the era after the
25
1994 Republican wave election; the substantive coefficient sizes are all comparable, although the
significances decrease due to the smaller sample size.
VIII. Evidence from Individual Vote Choice (CCES Data)
Having found that state ideology, candidate extremism, and seniority have asymmetric effects
on election results at the aggregate level, is remains to be explored whether we see the same effects at
work at the level of the individual vote. The question to be asked here is: do voters’ perceptions of
ideological distance and candidate experience affect their votes different based on the party of the
incumbent? If the asymmetric issue competence hypothesis is true, we would expect ideological
distance to have most effect on vote choice in the case of Republican incumbent, and experience to
have more effect on vote choice in the case of Democratic incumbents.
The data sets used in this section are the 2008 and 2010 Cooperative Congressional Elections
surveys, conducted over the internet in October and November of 2008 and 2010.7 Between the two
surveys, a sample of almost 90,000 American adults was assembled using a matching methodology.
Data, question wordings, and methodological details for the survey are available at
http://projects.iq.harvard.edu/cces/data. The advantages of this data set include both the very large
sample size and the inclusion of questions (although not consistent throughout the survey series) about
voters’ opinions on both sitting legislators and legislative candidates, such as questions asking about
perceived candidate ideology and voters’ stance on actual bills considered by the Senate.
For the purpose of this analysis in this section, “Ideological Distance” is the absolute value of a
respondents own ideological self-placement and their placement of the incumbent Senator running for
reelection (a 100-point scale in 2008, and a 7-point scale in 2010). “Not Experienced” references
7
I had also intended to use the 2006 CCES survey to provide a full cycle of Senate seat results, but the
appropriately analogous questions were not available in that year’s survey. Additionally, I was unable
to combine the results of 2008 and 2010 surveys into a single data set due to different coding scales
used on key variables (particularly ideological perceptions).
26
question CC317EE, “Do you consider this Candidate to be experienced” (in reference to an incumbent
running), taking a value of 0 for “Yes”, 1 for “No”, and .5 for “Don’t Know”; the question is asked
only in 2008. Only 6% of respondents overall answer “No” to this question in reference to
incumbents, making it of questionable value due to low variation, but it is the closest that the survey
gets to assessing voter opinions on a Senator’s seniority or legislative skill.
Table 7. Effect of Ideological Distance and Perceived Experience on Vote for Incumbent Senator
2008
Probit model
(1)
(2)
(3)
(4)
(5)
(6)
Vote for Incumbent
Dem
GOP
Dem
GOP
Dem
GOP
Ideological Distance
Not Experienced
Party ID (7 point)
State Fixed Effects
Constant
-0.046**
(0.0013)
-1.07**
(0.17)
-
-0.045**
(0.0011)
-1.50**
(0.12)
-
Excluded
2.96**
(0.18)
Excluded
3.11**
(0.13)
Observations
3,296
4,981
Standard errors in parentheses; ** p<0.01, * p<0.05
-0.032**
(0.0016)
-1.00**
(0.19)
-0.39**
(0.018)
Excluded
3.94**
(0.21)
-0.029**
(0.0015)
-1.15**
(0.14)
0.52**
(0.015)
Excluded
0.19
(0.17)
-0.033**
(0.0017)
-1.06**
(0.21)
-0.45**
(0.020)
Included
3.86**
(0.34)
-0.029**
(0.0015)
-1.11**
(0.14)
0.54**
(0.015)
Included
-0.68
(0.38)
3,264
4,942
3,146
4,942
2010
Probit model
Vote for Incumbent
(7)
Dem
(8)
GOP
(9)
Dem
(10)
GOP
(11)
Dem
(12)
GOP
Ideological Distance
-0.93**
(0.015)
-
-0.65**
(0.016)
-
Excluded
2.51**
(0.044)
Excluded
1.76**
(0.041)
-0.64**
(0.019)
-0.54**
(0.016)
Excluded
3.73**
(0.072)
-0.39**
(0.025)
0.70**
(0.021)
Excluded
-1.48**
(0.10)
-0.64**
(0.020)
-0.55**
(0.017)
Included
3.59**
(0.12)
-0.41**
(0.026)
0.71**
(0.022)
Included
-0.82**
(0.20)
9,551
4,585
9,551
4,514
Party ID (7 point)
State Fixed Effects
Constant
Observations
9,633
4,615
Standard errors in parentheses; ** p<0.01, * p<0.05
27
Table 7 provides no support for the issue competence hypothesis. In 2008, there appears to be
no difference in the impact of perceived ideological distance between support for Democrats and
Republican, and similarly little difference in the effect of perceived experience. In 2010, experienced
is not measure, and the effect of ideology is stronger on Democratic incumbents than on Republicans.
In both years, results are similar when Party ID and state fixed effects are included in the model. The
survey questions here may not be ideal measures (in particular the experience question has very little
variation), and results may be limited to the particular candidates running in key races in those years,
but there is no general support here for our thesis. Clearly, additional evidence is needed to link
different voter perceptions about issues to the effects observed in the aggregated results.
IX. Conclusion: Two Exceptions that Prove the Rule
The partisan issue competence theory suggests that Democratic senators perceived to have a
high proficiency at attaining state-specific benefits, often signaled by high seniority, will be extremely
difficult to defeat. And indeed this is supported by the data: among the 85 Democratic senators with
three or more terms of experience to run for reelection during 1984-2012, 82 were reelected.
But what of the remaining three? Two of the three were Tom Daschle of South Dakota, who
was defeated by John Thune in 2004, and Jim Sasser of Tennessee, defeated by Bill Frist in 1994.
These two senators had a lot in common: both had eighteen years Senate experience, both came from
conservative states and most importantly, they were both national party leaders. Daschle was minority
leader at the time of his defeat, and previously had been majority leader; Sasser was majority whip,
and with the retirement of George Mitchell in 1994, was certain to become majority (or minority)
leader had he been reelected. It seems that both candidates’ national prominence may have doomed
them.
Rather than being powerful voice for their home state, Daschle and Sasser became
representatives of their national party. Their conservative constituents perhaps no longer saw a vote
28
for Daschle and Sasser as a vote for state-specific benefits, but as a vote for the Democratic national
agenda. By becomes leaders of their party, Daschle and Sasser squandered the fortifications that their
party label and incumbency had provided in the past, and voters judged them on their ideology, like
they judged Republicans and open-seat candidates. And of course, Harry Reid might have become the
third such party leader defeated had his opponent in 2010 not been so extreme and gaffe-prone.
It thus appears that Daschle and Sasser are the exceptions that prove the rule. By virtue of
being identified by voters as the “pork party”, Democratic incumbents are resilient in the face of
ideologically distant constituents. And being the party of “national issues”, the Republicans are
subject much more to partisan and ideological scrutiny, particularly when they control the chamber. In
the past, Republicans have made up for this handicap by positioning themselves well, and outspending
Democrats, in open-seat contests. But should the Republicans remain at a disadvantage in incumbency
benefits, and not be able to sustain their advantage in open seats, as occurred in the 2008 and 2012
elections, the Democrats could maintain a long-term sizeable majority.
29
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