Objectives: The crucial question facing the contemporary abortion rights movement is why the gay and lesbian movement is winning and abortion rights is losing. Comparisons generally locate their divergent trajectories in the intrinsic nature of each movement’s claim, but research has not investigated how the histories and structures of each matter for their respective outcomes. Methods: I reviewed the literature on social movement outcomes and developed a theoretical framework for understanding social movement success. Then, drawing on published research and interviews with activists, I evaluated the two movements in terms of my theoretical framework. Results: Successful social movements have organizational diversity, resonant collective action frames, and favorable political and legal opportunity structures. While the gay and lesbian movement had all the components for success on same-sex marriage, the abortion rights movement has a homogeneous organizational structure, lacks a resonant frame, and faces hostile political and legal environments. Conclusions: Building from findings on what makes for social movement success, both theoretically and in the case of the gay and lesbian movement’s campaign for marriage equality, the abortion rights movement could improve its fortunes by increasing organizational diversity, notably by working through tensions with reproductive justice and clinician advocates, and by systematically investigating grassroots-generated frames to identify a persuasive alternative framing. Attending to the structure of the abortion rights movement is a useful way to assess its weaknesses and opportunities, and may offer practical guidance to advocates.