Voices & Choices

Shifts in Incumbency Advantage in the US House

Shifts in Incumbency Advantage in the US House

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Despite strong anti-establishment sentiment, which contributed to Donald Trump’s election and Bernie Sanders’ strong primary performance, more than 98% of U.S. House members won re-election in November. Not only were most incumbents re-elected, they were re-elected by significantly more comfortable margins than in 2014. The “incumbency bump” -- our measure of the strength of congressional incumbents -- rebounded from a 20-year low of 2.55% in 2014 to 3.2%. In other words, incumbents earned an average of 3.2 percentage points more of the vote than the partisanship of their district suggests they would earn.

While still low relative to what we’ve seen since we started tracking these figures in 1996, these numbers were boosted by a resurgence in incumbent advantage among Democrats from rock bottom levels in 2014 (less than 1%) to 2.77% in 2016. Meanwhile, incumbent advantage for Republicans fell from 4.5% to 3.8%.  These numbers reflect a national sentiment that at the congressional level was moderately favorable to Republicans, which will be discussed in an upcoming blog.


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In 2000, the nationwide incumbency bump was almost 8% and from 1996 to 2008 it had never gone below 5%. During this period, incumbents on average padded their victory margin by more than 10% over what would have been likely for their party in an open seat election. However, since 2008 the incumbency bump has fallen precipitously. Its minor resurgence this year does not make up much of the ground it has lost. What follows is an explanation of the incumbency bump, and what its decline means for our politics.

Defining the Incumbency Bump

Incumbents enjoy inherent electoral advantages over challengers, such as greater financial resources, more press coverage, more experienced campaign operations, past campaign outreach to voter, and ongoing delivery of constituent services for their districts. FairVote's “Monopoly Politics” U.S. House projection model quantifies the advantages of incumbency by comparing the electoral performance of incumbents to their districts' underlying partisanship. This "incumbency bump" measures the degree to which incumbents would outperform hypothetical generic candidates of the same party running in their district. It reflects earning the support of voters who would likely prefer the other party’s candidate for Speaker to run the House, but like the individual enough to support the candidate over the party.

Impact on Races

Incumbency bumps are largely irrelevant in most elections. While a completely open Congressional race field would cause a significant number of races to shift, the overall margins would change by only 8 seats towards Democrats. We projected the same number for 2016. However, in the shrinking number of districts with roughly even partisanship, this advantage can make a crucial difference, such that even districts with close to 50-50 partisanship are not actually competitive every 2 years, but only after retirements, political realignments, and new redistricting cycles.

Recent research suggests that the power of incumbency kept the U.S. House of Representatives majority Democratic for more than two decades after the political realignment that would culminate in the 1994 Gingrich revolution. Gingrich retook Congress for the Republican party on a decidedly anti-incumbent platform.

Since then, anti-incumbency sentiment has only increased, and yet the incumbent reelection rate for the House remains in the mid to high 90s. Explaining this disconnect also explains a central feature of the incumbency bump and why it continues to decline: The parties of House members have come to mirror more closely their district's' partisanship. The incumbency bump measures the extent to which incumbents outran their parties' presidential candidate in a given race, and there is much more room to outrun your party's presidential candidate in a district where he or she is unpopular. For this reason, congressional incumbents who outperform their parties' presidential candidates tend to be crossover representatives--a dying breed, both in the U.S. House and in state legislatures across the country.

The decline in the incumbency bump since 2010 also reflects a signature Republican accomplishment: the abolishing of earmarks. This significantly limited incumbent representatives’ ability to deliver funds to their districts, and many believe it sped up the polarization of the House by restricting incentives to cooperate with the opposition. Removing earmarks from the equation may have changed behavior at the ballot box as well, since senior House members could no longer leverage their power to bring more funding to their districts, limiting the financial incentives to stay with an experienced member over a more ideologically representative one.

Under other circumstances, the decline of incumbency advantage could be a good thing. After all, the incumbency advantage is just another way that competitive districts become uncompetitive, and temporary partisan trends get baked into the makeup of Congress. However, the decline in incumbency advantage over the past decade has so far imperiled precisely the kinds of representatives that are vital to the health of our democracy: moderates and unconventional partisans from crossover districts who can bridge the divides in our ever more partisan legislatures. Given that low incumbency advantage is unlikely to go away anytime soon, particularly with Congress’s approval rating still abysmally low, we need a new way of promoting unconventional representatives and ensuring they can get elected to begin with.

FairVote has a number of proposed reforms aimed at improving ideological and descriptive diversity within Congress, such as ranked choice voting and fair representation voting, which can be found on our website. For more information on partisan skew and noncompetitive districts check out our upcoming Monopoly Politics 2018 report, and our Monopoly Politics 2016 report.

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