In the context of congressional elections research on candidate competition, two lines of inquiry have received a considerable amount of scholarly attention. The first deals with the issue of strategic candidate emergence in seeking to identify the conditions under which experienced candidates will challenge incumbents. The second focuses on the question of incumbents’ career choices, particularly in terms of their decisions to seek reelection or retire. While past research has treated these questions as mutually exclusive, I argue in this article that such explanations are incomplete due to the complementary nature of the approaches. To unify these related research agendas, I develop a theoretical model of strategic interaction between congressional challengers and incumbents and test the model with House and Senate elections data from 1976 to 2000 using a strategic probit technique. The results both confirm and challenge a number of findings in the literature on candidate competition.