Civil society is laying claim to political representation in contemporary democracies, destabilizing long-standing ideas about democratic legitimacy. The participatory governance structures that have emerged alongside classic institutions of representative democracy encompass not only direct citizen participation but also political representation by civil society actors. Using original data from São Paulo, Brazil, we show that most of civil society actors that work for the urban poor claim political representation of their “constituency.” Theirs is more often than not an “assumed representation,” we suggest, because our data show that most lack formal members and do not select leaders through elections. Civil society actors (in contrast to political parties and labor unions) lack historically settled and politically sanctioned mechanisms to authorize and hold accountable their representation. This new layer of political representatives therefore faces a historic challenge—constructing novel notions of democratic legitimacy that can support their forms of representation. We examine what new notions of representations are emerging and trace the historic roots of the most widespread and promising that focus on remedying inequality in access to the state.