This paper examines the role that democratic organizations play in fostering political activism in America. Activists make democracy work by attending meetings, engaging others, trying to make their voice heard, and participating in myriad other ways. Yet we have a limited understanding of what role organizations play in cultivating that activism. The paper presents data from three field experiments showing that creating a relational organizational context makes targets more likely to sign petitions, recruit others, and attend meetings. The paper argues that civic organizations can have a powerful impact on activism. In doing so, it challenges individualistic models of participation and introduces a new set of variables related to organizational context to consider in understanding the sources of participation. The paper thus extends a burgeoning body of experimental research on voter mobilization to examine forms of activism that are increasingly common modes of citizen involvement in the twenty-first century.