The United States boasts scores of organizations that offer crucial representation for groups that are marginalized in national politics, from women to racial minorities to the poor. Here, in the first systematic study of these organizations, Dara Z. Strolovitch explores the challenges and opportunities they face in the new millennium, as waning legal discrimination coincides with increasing political and economic inequalities within the populations they represent. Drawing on rich new data from a survey of 286 organizations and interviews with forty officials, Strolovitch finds that groups too often prioritize the interests of their most advantaged members: male rather than female racial minorities, for example, or affluent rather than poor women. But Strolovitch also finds that many organizations try to remedy this inequity, and she concludes by distilling their best practices into a set of principles that she calls affirmative advocacy - a form of representation that aims to over-come the entrenched but often subtle biases against people at the intersection of more than one marginalized group. Intelligently combining political theory with rigorous empirical methods, "Affirmative Advocacy" will be required reading for students and scholars of American politics.