How does the state ensure the implementation of national policies in a context of decentralized political authority? This article identifies a new strategy utilized by national bureaucrats to regulate the behavior of subnational politicians: mobilizing civil society as government watchdog and political advocate. In the context of decentralized governance, in which local politicians administer most social sector programs, reform‐minded bureaucrats often find that they have little control over the implementation of their progressive policies. In Brazil's AIDS policy sector, however, bureaucrats have ensured the successful implementation of their policies by developing allies outside government. These state actors—here called activist bureaucrats—have been largely overlooked in the English‐language literature, yet they form a new layer of politics in Latin America.