This paper analyzes the rise and decline of social movements in Amsterdam and Paris, focusing in particular on the organizations of left-wing immigrant workers. These organizations performed crucial roles for new social movements in the 1970s and 1980s but were isolated and coopted in the 1990s and early 2000s. To explain why this is so, we engage in a dialogue with Jacques Rancière and develop an understanding of cities as strategic sites for both politicization and policing. Cities serve as sites of politicization because they are incubators of the relational conduits that enable activists from different sectors to engage with one another's struggles and look beyond narrow temporal and spatial horizons. However, cities also serve as sites of policing because authorities constantly attempt to reconfigure governmental arrangements in such a way that civil society serves as an extension of the government and comes to fulfill an instrumental role in the development and implementation of policy. Just as politicizing implies the widening of temporal and spatial horizons, policing implies the narrowing of such horizons. The analysis shows the social movements of the 1960s lost steam in two of the major hubs of the new left and reveals some of the more universal mechanisms through which cities generate or quell dissent.