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Carson, Engstrom, and Roberts: Candidate quality, the personal vote, and the incumbency advantage in Congress

Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.

Carson, Jamie L., Erik J. Engstrom, and Jason M. Roberts. 2007. Candidate quality, the personal vote, and the incumbency advantage in Congress. American Political Science Review 2 (May): 289-301.

In Brief

The authors seek to answer two questions about 19th century Congressional (House) elections:

  1. Was there an incumbency advantage, even before members of Congress had large staffs (for casework), the frank, high salaries, and constant redistricting on their side?
  2. If so, to what extent did this advantage merely reflect the incumbent's ability to scare off potential challengers?

By asking these two questions, Carson et al. seek to shed greater light on our understanding of the incumbency advantage--an understanding based on the post-WWII experience. By examining another historical period, the authors are able to vary more of the variables than most studies can vary.

They find that there was an incumbency advantage--for whatever reason--and that it was, in fact, magnified by a "scare-off" effect. Cox and Katz claimed that this scare-off effect explained the rise in the incumbency advantage over recent decades; the authors claim that Cox and Katz may have identified a true effect but that the effect cannot explain the recent rise since the effect was present a century ago.

Place in the Literature

Previous authors have offered three types of explanation for the Congressional incumbency advantage:

  1. Perks of office, such as the frank and opportunities for casework (Fiorina 1977)
  2. Gerrymandering and weakened party identification (Erikson 1972)
  3. An ability to scare off the best potential challengers (Cox and Katz 1996, 2000)

Cox and Katz actually had a two part candidate-quality effect. They claimed that incumbents were high-quality candidates (evidenced by their previous victory) and that they were able to scare off good challengers. In part, incumbents can use redistricting to separate themselves from their most threatening potential challengers, and in part, incumbents simply deter many opponents from running.

By studying historical (1870-1900) House elections, Carson et al. eliminate the first two theories, which are based on recent trends. They also challenge the third theory; Cox and Katz see their theory as explaining why the incumbency advantage increased since 1964 (as a result of the Court's "one person, one vote" ruling that led to constant redistricting).

Theoretical Argument

Much of the authors' theory merely applies previous arguments from the literature. However, they do find themselves needing to defend one particular point. Late 19th century elections were much more party-centered than today's candidate-centered affairs. With party leaders selecting Congressional candidates--and with voters using party-printed tickets--should we even expect candidate quality to matter in this era? Jacobson (1989, 787) argues that we should not.

The authors respond to this challenge by discussing the competing incentives of parties and candidates. As for candidates, it is now accepted that Congressional election results depend crucially on challenger quality. When national partisan tides (and district-level concerns) favor an incumbent's party, she is unlikely to attract a well-funded, experienced challenger (Jacobson and Kernell 1983). After all, potential challengers must bear costs to run--such as placing their political career at risk--so the best challengers will run only when success seems likely.

Carson et al. remind us, however, that parties have the opposite incentives. When the national tide favors the Democrats, the Republican party wants to recruit the best possible challengers in an effort to forestall the pro-Democratic tide. In our candidate-centered era, however, the party rarely gets its way--candidates choose whether to run.

In the late 19th century, before the progressive reforms brought popular primaries to the electoral scene, challengers were selected by local party leaders. And these leaders had control of pork, patronage, and other enticements that they could use to persuade high-quality challengers to run even against the partisan tide. Still, self-interested politicians still could refuse to run. So we should expect the same variations in challenger quality that we observe today.

Moreover, parties needed these challenger candidates. Even though voters used party-printed ballots, the authors present anecdotal evidence to suggest that it was the Congressional candidate's quality--not the presidential candidate's--that influenced voters the most.

Empirical Evidence

The authors seek to predict the Democratic candidate's vote share as a function of the lagged vote, the incumbent's party (also lagged), a dummy for whether an incumbent was present (the primary coefficient of interest), and the Democratic quality advantage (a dummy indicating which party had the more experienced candidate; also lagged). They find that both incumbency and quality matter.

They then predict the Democratic quality advantage using essentially the same variables, and find that an incumbent's presence lowers the likelihood of a quality challenger.

Research by the same authors

Research on similar subjects


Roberts, Jason M. (author)Engstrom, Erik J. (author)Carson, Jamie L. (author)American PoliticsElectionsChallenger QualityIncumbency AdvantageState Politics (U.S.)Primary ElectionsCongress (U.S.)

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