Parties have historically been platforms for a variety of social movements, from the religious right to the women’s movement, yet little research has focused on how movements and parties interact. Using the framework of political opportunity structure, I examine how differences in party organizations within the United States lead to variation in protest mobilization. As parties become more open to new issues and activists, movement actors will prefer traditional forms of political participation and shun the use of protest. I test this using United States primary election laws at the state level, as they constrain the party’s control over candidate selection. My dependent variable is protest counts drawn from the Dynamics of Collective Action dataset. Examining the period from 1976 to 1995, I find evidence of increased protest activity in states with semi-closed primaries where activists have only some access to candidate selection.
