The ProDem team presents at the ECPR General Conference September 2021 a joint paper. This conceptual exploration of how the triple interaction between citizens, social movements, and movement parties influences democratic quality in Europe lays out the theoretical groundwork for the Consortium’s future research. By placing the triple interaction between protest and institutional arenas, ProDem theorizes democratic quality as comprising the dimensions of participation, competition, and responsiveness. This analytical framework allows us to assess how the triple interaction influences: a) democratic participation by institutionally and extra-institutionally mobilizing citizens who were previously disengaged from politics; b) competition by polarising public debates on sensitive issues by delegitimising traditional sources of information in the media, as well as linkages to political elites and movement actors; and c) responsiveness of political institutions and the media including new political demands. This novel understanding of democratic quality between protest and institutional arena may contribute by insights into the interaction of citizens, social movements and movement parties and parliamentary politics. In doing so, it will enable us to assess democratic quality in the current turbulent climate where extra-institutional participation may play an increasingly important role.