Master of Arts (MA)


Political Science

Document Type



Why do legislators switch parties? What accounts for variation in party switching across different countries? How do electoral rules impact legislative party switching behavior and how is this behavior impacted by changes to these rules? The first chapter of this study builds on the existing body of research on the determinants of legislative party switching. More specifically, I build on the extant theories which have identified vote-, office-, and policy-seeking as motivations of legislator behavior. I examine the strategic decision making of legislators in various institutional contexts and argue that such contexts create or modify incentives and constraints that condition the decision to switch parties. Moving beyond the single country and cross-national party level analyses prevalent in the literature, this study attempts to approach party switching with a cross-national battery of variables from an original individual-level dataset. This dataset includes observations from Canada, Italy, New Zealand, and the United Kingdom from 1990-2001. I find support for vote- and policy-seeking hypotheses as well as district and system level institutional variables. In order to investigate how electoral rules impact party switching behavior, the second section of this study focuses on New Zealand and the evolution of its electoral system. These changes include a transition from a pure single-member district (SMD) electoral system to a mixed-member (MM), compensatory proportional representation system in 1996. Preliminary evidence suggests that the change to a MM electoral system is associated with a rise in the frequency of legislative party switching in New Zealand's House of Representatives. Additionally, there is evidence that party switching legislators are motivated by vote-seeking concerns over reelection.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kerevel, Yann