Incumbency Disadvantage under Electoral Rules with Intraparty Competition: Evidence from Japan

Many studies have shown that incumbent candidates have an electoral advantage over nonincumbents under single-member-district systems, but less is known about whether incumbents enjoy the same electoral bonus under other electoral rules. This article focuses on multimember-district systems that allow intraparty competition and contends that incumbents may have little advantage or even a disadvantage over nonincumbents of the same party under these systems, although the incentives to cultivate a personal voteone of the main sources of incumbency advantageare greater in these systems. I demonstrate my argument using electoral data from Japan during 1958-93 when the country used the single nontransferable vote system. Having applied an estimation of incumbency advantage immune to endogeneity bias due to strategic retirement, I find supportive evidence to my argument. The results suggest that there is an important variation in incumbency advantage across electoral systems.