These quotations are an apt synopsis of the main theoretical assumption I make in this book. Having witnessed a number of Democratic officeholders defecting to the Republican Party during the 1990s, former Democratic representative (and political science professor) Glen Browder made his observation after Republicans had approached him about possibly switching sides. What struck Browder was the extent to which many party switchers failed to be embraced immediately by their new party, as well as the animosity felt by former co-partisans they left behind. As a politician from Alabama and a scholar of southern politics, Browder had a front-row seat to appreciate the dynamics surrounding party switching, and he noticed that incumbents who switched parties were often attacked from both sides.

The idea that switching parties entails significant costs is not the dominant paradigm in the literature. To the contrary, the received wisdom is that politicians incur benefits at the polls by switching into the “correct” party in terms of their constituency (Aldrich and Bianco 1992). This intuitively makes sense, as it is reasonable to expect reelection-seeking politicians to bolt to the other party when doing so increases their chances of getting reelected. Policy motives also figure prominently in explanatory models of party switching (Castle and Fett 2000). Yet most politicians, even those in electoral jeopardy or who are cross-pressured ideologically, do not switch parties.