My research and teaching focus on the ways that institutions constrain the choices of political actors. I also explore the ways that institutions evolve and change due to actor choice. My early work as a political scientist analyzed leadership and alliances in union organizations. I have studied opinion coalitions in the judicial arena. My first single-authored book (The Costs of Coalition, Stanford 2002) and associated publications examined coalition executives in parliamentary democracies. I am currently engaged in two research projects: one on the causes and consequences of party switching among legislators (funded by the National Science Foundation); and the other, related to the first, on sources of change in democratic party systems. In all of my research, I am interested in how and why elected representatives (in the judicial research, non-elected guardians of the law) form and rupture alliances in efforts to get what they want. While many of my publications concentrate on Western Europe, my teaching and my current research include empirical evidence from the United States, Japan, Russia, and Brazil. For further details on my professional background, see my personal website.