Gordon and his colleagues take this widely accepted argument a step further. Their concern lies not with the candidates’ thinking, but with the voters’. If, as previous research indicates, high-quality challengers act strategically when deciding whether to run against a Congressional incumbent, then this decision ought to convey important information to voters.

As long as voters believe that the challenger actually bears the sort of costs discussed in the literature,¹ then the challenger’s willingness to incur these costs signals to voters that the incumbent may be weak.²

Democracy is supposed to provide voters with an opportunity to hold elected officials accountable for their performance in office. With so many elected officials to monitor, however, voters would have a difficult time fulfilling this task without assistance. We have long known that challenger behavior assists voters in this judgment by determining whether voters even have a real choice to make on election day. Gordon and his colleages add to this argument by explaining that challengers also provide information to voters about the incumbent’s performance merely by deciding whether to run.

This study builds on two fields. First, it seeks to develop our understanding of retrospective voting (Fiorina 1981; Kramer 1971). Second, it contributes to the literature on the incumbency advantage and challenger quality (Cox and Katz 1996; Jacobson and Kernell 1983).

The authors present no empirical evidence to support their claims, only a formal model. Given the large body of literature already available about strategic entry, this approach is not bothersome–yet. Personally, however, I hope to see empirical evidence for these arguments in future research. The claims make good sense, but sensible, intuitive claims often lead to unexpected, counterintuitive findings when tested on real-world data.

What is less clear is the source of this incumbency advantage. Previous research has suggested three answers. First, perhaps the perks of office, particularly the franking privilege and opportunities for casework, allow incumbents to endear themselves to their constitutions (Mayhew 1974; Fiorina 1977). Second, perhaps gerrymanding and weakened party loyalty are to blame (Erikson 1972). Or third, perhaps incumbents are so formidable that the best potential challengers simply refuse to invest their time running (Cox and Katz 1996; 2000).²

The trouble with these theories is that they have been developed and tested in the post-World War II context. Carson et al., by contrast, look to historical (1870-1900) House elections for further illumination. In so doing, they cast doubt on the first two theories, both of which claim that factors present today (but absent in the nineteenth century) cause the incumbency advantage. As it turns out, there was an incumbency advantage even then, even before members of Congress had large staffs (for casework), the frank, high salaries, and constant redistricting.

The authors then turn to the third theory. Cox and Katz supposed that their “scare-off” theory explained why the incumbency advantage had strengthened since 1964, the year of the Supreme Court’s “one man, one vote” ruling that led to perpetual redistricting. However, Carson et al. find 19th-century evidence of the same “scare-off” effect that Cox and Katz observed post-1964. Thus, although Cox and Katz may have identified a true effect, their “scare-off” effect cannot explain the recent rise in the incumbency advantage since the effect was present a century ago, long before “one man, one vote” took effect.

Candidate Quality in the Nineteenth Century

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 (rather than candidates openly competing in primaries) 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 reason lies in 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. The trouble is, 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 the party rarely gets its way, giving rise to the literature on challenger entry. But in the party-centered era that Carson et al. study, the criticism goes, we should not expect challengers to behave strategically; party leaders had pork, patronage, and other enticements that they could use to persuade high-quality challengers to run even against the partisan tide.

Carson et al. dismiss this concern, noting that self-interested politicians could refuse to run despite these incentives. Therefore, we should expect the same variations in challenger quality that we observe today–making the “scare-off” effect a reasonable thing to expect in the late nineteenth century. Moreover, candidate quality did matter, the authors claim; 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.

The Main Point

In case you missed it, here it is: Previous researchers have advanced three main arguments in an attempt to explain the origins of the incumbency advantage. But although their arguments may be true to an extent, they cannot be the full story. The first two theories depend on conditions that were not present in the nineteenth century, yet the incumbency advantage was–therefore, they cannot be the complete explanation. And the third theory claims to explain the increasing power of the incumbency advantage since the 1960s, yet it was present in the nineteenth century–so something else must account for the increasing advantage.

The main point: We still don’t know everything about what causes the incumbency advantage, so we need more research into it.