The better-known cases of party switching may be found at the national level (e.g., Arlen Specter, Jim Jeffords), but elite party switching is not confined to the halls of the U.S. Congress. Following the 2010 midterm elections, for instance, a number of state legislators – many of them conservative southern Democrats – decided the time was right to bolt to the Republican Party. Those cases of party switching were widely reported in the media as an indication that on the heels of its historic landslide victory, the GOP had the wind at its back. Theoretically any sitting politician at the national, state, or local level can decide to switch partisan stripes. These numerous opportunities for party switching at all levels of government in the United States can then be leveraged to inform our theoretical understanding of the phenomenon. With a much wider pool of potential party switchers, states legislatures represent another arena in which I can test some empirical implications of my theoretical framework.

From the perspective of testing theories of elite decision making, the many cases of party switching at the state level offer at least three distinct advantages. First, we can examine whether the theory and findings from the congressional analyses are generalizable to other settings across time and space. Second, the data allow for more precise estimates if only because of the larger number of cases. Third, as one of the main launching pads for a national career (Berkman 1993; 1994; Canon 1990; Maestas, Maisel, and Stone 2005; Maestas et al. 2006; Schlesinger 1966), state legislatures are an incubator for ambitious politicians with national aspirations. Party switching among state legislators therefore has implications that can spill over to the national stage because it directly affects one of the main pipelines of viable congressional candidates.

This chapter serves a very specific goal: to further our understanding of party switching by testing one implication of the theory in the state legislative arena, namely the role of progressive ambition in fueling party switching. The central motivation for this chapter, then, is to test a causal mechanism of the theory with systematic data from an entirely different setting. In short, I examine whether the progressive ambition hypothesis finds support at the state level. In addition, this chapter offers detailed descriptive accounts of specific instances of party switching at the state level.