Why do social organizations decide to protest instead of working through institutional channels? This book draws hypotheses from three standard models of contentious political action - POS, resource mobilization, and identity - and subjects them to a series of qualitative and quantitative tests. The results have implications for social movement theory, studies of protest, and theories of public policy/agenda setting. The characteristics of movement organizations - type of resources, internal leadership competition, and identity - shape their inherent propensity to protest. Party alliance does not constrain protest, even when the party ally wins power. Instead, protest becomes a key part of organizational maintenance, producing constant incentives to protest that do not reflect changing external conditions. Nevertheless, organizations do respond to changes in the political context, governmental cycles in particular. In the first year of a new government, organizations have strong incentives to protest in order to establish their priority in the policy agenda.