Publication Type: Conference Paper/Unpublished Manuscript Abstract: The purpose of this study is to evaluate the relationship between political party systems and social movement activity comparatively after the third wave of democratization. Through a cross-country comparison of 38 countries, we find that citizens are more likely to use contentious tactics in states with plurality elections where the party system is less open to change with a changing salient issue environment. Consistent with this finding, as the effective number of political parties in the legislature increases, the level of contentious social movement activity decreases in a country. In more flexible electoral system with a higher number of political parties, we find less protest activity, indicating that political parties effectively fulfill their role of representing different constituencies and maintaining relationships with organized groups. Constituencies are more likely to seek the attention of the authorities through protest activity where there are limited number of parties with all encompassing agendas and an electoral system that limits party entry into the system.