We develop a model of strategic interaction between voters and potential electoral challengers to sitting incumbents, in which the very fact of a costly challenge conveys relevant information to voters. Given incumbent failure in office, challenger entry is more likely, but the threat of entry by inferior challengers creates an incentive for citizens to become more politically informed. At the same time, challenges to incumbents who perform well can neutralize a voter's positive assessment of incumbent qualifications. How a voter becomes politically informed can in turn deter challengers of different levels of competence from running, depending on the electoral environment. The model permits us to sharpen our understanding of retrospective voting, the incumbency advantage, and the relationship between electoral competition and voter welfare, while pointing to new interpretations of, and future avenues for, empirical research on elections.