This study analyzes a new form of political mobilization in Latin America--in which social movements make aggressive policy demands on the state, even while relying on the state for financial support. This model of interest intermediation runs contrary to existing theories of social movements and interest groups, which predict that organizations will moderate their demands and activities as a consequence of state funding.I explain the development of this new model of interest intermediation through an analysis of AIDS advocacy in Brazil, one of the most widely-acclaimed cases of sustained grassroots mobilization in Latin America. Through a combination of cross-temporal and subnational comparison, I show that this current pattern of interest mobilization developed in response to a new and understudied political actor in Latin American politics: activist bureaucrats. In the context of decentralized governance, in which local politicians administer most social-sector programs, reform-minded bureaucrats often find they have little control over the implementation of their progressive policies. In Brazil's AIDS policy sector, however, activist bureaucrats have ensured the successful implementation of their policies by developing allies outside the state: mobilizing civil society groups to monitor the actions of local politicians and pressure them to conform to national policy guidelines.AIDS bureaucrats launched this grassroots-style campaign through two key mechanisms: (1) by providing resources and institutional opportunities for new civic associations to participate in the political arena, and (2) by supporting the endeavors of social movement leaders to mobilize new civic AIDS associations as political actors. As a result of this training and support, Brazil's civic AIDS organizations rely as much on contentious strategies for making claims on the state as they do on insider lobbying strategies. By showing how specific actors within a heterogeneous state can play a constructive role in interest mobilization, this dissertation provides a major refinement to the existing theories of social movements that emphasize autonomy from the state as key to effective demand-making.