Chapter 2 introduces the concept of party fit and discusses how ideological conformity with the party influences the value of the office and the calculus of candidacy. It provides the theoretical framework for why moderates have opted out of the congressional candidate pool in the contemporary context. Interviews with former members of Congress illustrate how the ability of moderates to influence policy, advance within the chamber, and forge bonds with their fellow co-partisans diminished as the parties drifted apart. I also address how patterns of candidate emergence contribute to aggregate party change over time and how the abstention of moderates from congressional politics has contributed to partisan polarization. Chapter 2 concludes by examining electoral considerations. I analyze whether a larger proportion of moderate candidates run in districts where they should be more likely to win. There is little variation in candidate entry across different types of districts that would be more and less favorable to moderate candidates, and this variation has only continued to decrease over time.