In recent years, there has been an explosion of legislative and litigation campaigns to ban conversion therapy for sexual orientation and gender identity. In championing such bans, the American LGBTQ+ advocacy movement has incorporated its massive network of scientific and medical allies into legal arguments, legislative testimonies, educational materials, and political cultural discourse more generally. By linking these recent campaigns to the long history of scientific influence in LGBTQ+ politics, I demonstrate how biomedical and mental health institutions and ideas have become foundational to the character of American LGBTQ+ advocacy. I do so by marrying theories and methodological approaches to studying political identity and social movements, American political development, and public opinion to those in Science and Technology Studies (STS) and biopolitical citizenship studies. This joint perspective reveals both the power of scientific authority as well as the political, legal, and normative pitfalls that attend certain biomedical articulations of identity and personhood, legal rights claims, and demands for full and equal citizenship. This approach demonstrates how scholars might conceptualize and study the role of extra-political institutions and ideas that become constitutive components of minority rights coalitions.