Challenger Quality and the Incumbency Advantage

Most estimates of the incumbency advantage and the electoral benefits of previous officeholding experience do not account for strategic entry by high‐quality challengers. We address this issue by using term limits as an instrument for challenger quality. Studying US state legislatures, we find strong evidence of strategic behavior by experienced challengers. However, we also find that such behavior does not appear to significantly bias the estimated effect of challenger experience or the estimated incumbency advantage. More tentatively, using our estimates, we find that 30–40% of the incumbency advantage in state legislative races is the result of “scaring off” experienced challengers.