Do the advantages of incumbency advantage incumbents?

We develop a model that calls into question some longstanding presumptions about incumbency advantage. Our results show that increases in some of the ostensible benefits of incumbency frequently cited in the empirical and theoretical literature make it difficult for voters to differentiate incumbents of higher and lower quality. While this leads to an improvement in the electoral prospects of lower-quality incumbents, it is harmful to those of higher quality. Whether the net electoral consequence for high-quality incumbents is positive or negative depends on whether the source of incumbency advantage affects candidate entry and exit decisions directly or indirectly, as mediated through voters choices. Our findings suggest, further, that fundamental tensions may exist between different sources of incumbency advantage, and point to obstacles to disaggregating the sources of incumbency advantage empirically.