Old voters, new voters, and the personal vote: Using redistricting to measure the incumbency advantage

We provide new estimates of the size of the personal vote in U.S. House ele ctions from 1872 to 1990. We take advantage of the "natural experiment" tha t attends decennial redistricting every ten years, most incumbents are give n new districts that contain a combination of old and new territory. By con trasting an incombent's vote in the new part of the district with hist or h er vote in the old part of the district, we can estimate the magnitude of t he personal vote-the vote that the incumbent receives because he or she rep resented the voters in the past. Our estimates confirm prior work that show s that a large fraction of the incumbency advantage owes to the personal vo te, as opposed to challenger quality. Unlike past research, we are able to estimate the relationship between district partisanship and the personal vo te. We find a significant interaction which shows that incumbents develop l arger personal votes in areas where they are electorally most vulnerable.