Political institutions often provide rights and protections for particular groups (e.g., refugees, groups who faced historical discrimination). Who belongs to a given group, however, can be contested. We study the politics of social categorization by focusing on transgender women’s athletic participation in the United States. We offer a framework that integrates work on frames and work on group categorization. We predict a substantial change in attitudes about transgender women’s athletic participation between 2019 and 2024 – a period during which the issue became highly politicized with the emergence of an exclusion frame. We use unique cross-sectional data from those years to show that support for transgender women’s participation substantially dropped. Strikingly, among Republicans, the relationship between support for a non-discrimination policy (Title IX) and support for transgender women’s sports participation flipped from positive to negative: support for a non-discrimination policy correlated with exclusion beliefs in 2024. The findings highlight how existing non-discrimination policies can become mechanisms of category exclusion when the contested group is framed and then perceived as a threat to historic stakeholders.
