Political protest and collective action is everywhere. Drawing on a chapter in the 2013 Oxford Handbook of Political Psychology, we discuss the mechanisms of engagement and disengagement in collective action as they are currently conceived in social and political psychology. We will decompose the dynamics of collective action into dynamics of demand, supply, and mobilization. Dynamics of demand are about people and their motives, dynamics of supply about organizations and their appeals, and dynamics of mobilization about the convergence of demand and supply. So far, the core business of political psychology has been the demand-side of protest. We describe 5 core concepts affecting collective action participation: grievances, efficacy, identity, emotions, and social embeddedness. As for the supply side of protest and mobilization new research lines (framing, the perceptions of the socio-political context, and the role of social media for dynamics of mobilization and participation) are discussed. We close with a discussion of new directions research methodology has taken.
