Why do political incumbents have an advantage?

Most political observers agree that incumbent legislators have a considerable advantage over nonincumbents in modern congressional elections. Yet there is still disagreement over the exact source of this advantage and the explanation for its growth over time. To address this debate we utilize a unique set of historical elections data to test for the presence of an incumbency advantage in late-nineteenth-century House elections (1872â1900). We find a modest direct effect of incumbency and a substantial candidate quality effect. Moreover, the cartel-like control of ballot access by nineteenth century political parties created competition in races that the modern market-like system simply does not sustain. Our results suggest that candidate quality is a fundamental piece of the puzzle in understanding the historical development of the incumbency advantage in American politics.

Source: “Candidate Quality, the Personal Vote, and the Incumbency Advantage in Congress” from American Political Science Review (2007), 101:2:289-301 American Political Science Association