Why Did the Incumbency Advantage in U.S. House Elections Grow?

Abstract

Theory: A simple rational entry argument suggests that the value of incumbency \nconsists not just of a direct effect, reflecting the value of resources (such as staff) \nattached to legislative office, but also of an indirect effect, reflecting the fact that \nstronger challengers are less likely to contest incumbent-held seats. The indirect \neffect is the product of a scare-off effect-the ability of incumbents to scare off \nhigh-quality challengers-and a quality effect-reflecting how much electoral advantage \na party accrues when it has an experienced rather than an inexperienced \ncandidate. \nHypothesis: The growth of the overall incumbency advantage was driven principally \nby increases in the quality effect. \nMethods: We use a simple two-equation model, estimated by ordinary least-squares \nregression, to analyze U.S. House election data from 1948 to 1990. \nResults: Most of the increase in the incumbency advantage, at least down to 1980, \ncame through increases in the quality effect (i.e., the advantage to the incumbent \nparty of having a low-quality challenger). This suggests that the task for those \nwishing to explain the growth in the vote-denominated incumbency advantage is \nto explain why the quality effect grew. It also suggests that resource-based explanations \nof the growth in the incumbency advantage cannot provide a full explanation.