The Source of the Incumbency Advantage in the U.S. House (1956-2020)

• In Event: Party Loyalty across Contexts and Commitment Levels

Abstract

Which voters drive the incumbency advantage? Are partisan voters as sensitive to the incumbency status of candidates as independent voters? Partisan voters are widely considered to be extremely rigid in their voting behavior, rarely if ever voting for out-partisan candidates, but incumbents from both parties enjoy a large electoral advantage. In this paper, I argue that the source of the incumbency advantage is primarily partisan voters, and that voters’ sensitivity to incumbency status may be explained by their lack of information about candidate quality. Drawing on data on US House election returns and self-reported vote choice from 1956-2020, I employ a close-election regression discontinuity design to obtain estimates of the incumbency advantage across subgroups of voters defined by partisanship and interest in politics. Although I find that the effect of incumbency on vote choice is higher among independent voters than partisan voters, the latter make up a much larger share of the electorate, thereby contributing most to the incumbency advantage. I also report suggestive evidence that the effect of incumbency on vote choice is larger among voters that pay less attention to politics. My findings improve our understanding of the incumbency advantage and voting behavior by demonstrating that the voting behavior of partisan voters drives the incumbency advantage, and providing suggestive evidence that subsets of both partisan and independent voters may choose incumbents because they lack useful information about candidate quality other than incumbency status.

Author

• Jacques Courbe, University of California, Los Angeles