Old Voters, New Voters, and the Personal Vote: Using Redistricting to Measure the Incumbency Advantage

Abstract

We provide new estimates of the size of the personal vote in U.S. House elections from 1872 to 1990. We take advantage of the natural experiment that attends decennial redistricting: every ten years, most incumbents are given new districts that contain a combination of old and new territory. By contrasting an incombent's vote in the new part of the district with his or her vote in the old part of the district, we can estimate the magnitude of the personal vote-the vote that the incumbent receives because he or she represented the voters in the past. Our estimates confirm prior work that shows that a large fraction of the incumbency advantage owes to the personal vote, as opposed to challenger quality. Unlike past research, we are able to estimate the relationship between district partisanship and the personal vote. We find a significant interaction which shows that incumbents develop larger personal votes in areas where they are electorally most vulnerable. here is no doubt that incumbents today have a substantial advantage over nonincumbents in U.S. House elections. The overall size of this advantage has been fairly well established, as has the fact that incumbents' electoral strength has increased dramatically over the postwar period. Measured in terms of vote share, the overall incumbency advantage grew from a modest 1-3 percentage point edge in the 1940s and early 1950s to a 7-10 percentage point edge in the 1980s and early 1990s.1 There is much less agreement about the sources of the incumbency advantage and the causes of its growth. Congressional scholars have identified a variety of factors that may be responsible, which can be grouped into three broad categories. The first, and the focus of this paper, is electoral advantage that stems from a legislator's homestyle. Members of the House are reputedly very responsive to their constituents; in turn, their constituents reward them with their votes. Mayhew (1974b), Fenno (1974), and others detail the sorts of activities that legislators do to build a widely known and respected name, including casework, frequent visits to the district, position-taking on issues, and securing federal benefits. A second source of the incumbency advantage is candidate quality. Incumbents may win because they are the best candidates running, and they do noticeably worse when they face state legislators and other experienced challengers. Finally, incumbency may simply act as a voting cue, a label which voters rely on because party has become less relevant. Assessing the importance of these different factors has significant implications for our normative evaluations of the modern congress and our understanding