The Greek epicenter of the Eurozone crisis was violently shaken by one of the deepest economic depressions of the past century. The call for financial assistance by the 2010 Greek government resulted in a series of bailouts whose conditionality and policy requirements deeply divided Greeks for the next eight years. This thesis deals with the dismantling of the Greek party-system during the Eurozone crisis, in conjunction with the volatile outburst of one of the proportionally largest protest campaigns in post-war Europe. The Greek case is interesting firstly due to its unique outlier status in multiple dimensions, like the depth of economic crisis, the unique mass scale of protest and party-system change. But beyond the case specifics, the thesis uses the Greek case as a unique contemporary vantage point to understand patterns of interaction between large-scale contentious and institutional politics and the mechanisms of abrupt party-system change. To study contentious institutional interactions, a novel framework is proposed, examining the Greek case through the detailed narration of four contentious episodes, streams of interactions among government, challengers and third parties around contested policy packages, the bailouts. This methodological novelty is complemented by a theoretical framework that conceptualizes the bailout-induced change in structures of policy-making and political competition, and thus the context within which the protest wave unfolded. The thesis follow the evolution of escalating protest and party-system unraveling through the succession of contentious episodes to detect the mechanisms through which they interact. I draws attention mainly to indirect mechanisms through which social movements influence party-system outcomes, namely elite breakdown and paralysis and the reconfiguration of dimensions of political conflict. Additionally, the dissertation delimits the effect of social movements mostly on those indirect effects. To complete the story of party-system punctuation, I expose critical elements of agency and structure unrelated to protest, such as the bailout’s opportunity structure, shrewd party positioning and the revealing of the mental (mis)calculations of institutional protagonists, which are the other required elements to guide us through the process of Greek party-system implosion. The final chapters eventually expand on how this punctuation was overcome, this time by reference to the missing contentiousness and the ways Syriza used persuasion, its profile as a new party and its leader’s popularity to avoid a repetition of the first cycle of contention, bringing the crisis full circle.