This article draws on field theory to explain why leftist parties in Brazil first broached debates on homosexual liberation in the late 1970s and early 1980s. The concept of a cultural field allows one to bring together both an institutional and a cultural analysis of changing debates in the left, casting light on processes of contestation often obscured in the institutionalist party literature. Electoral institutional changes and the emergence of a new generation of cadres, particularly from the student movement, fundamentally changed who and what were representable in the field. The emergence of a youth counterculture also expanded the discursive repertoire available to activists and their party allies, supported by debates in Marxist circles occurring internationally. This conjuncture of forces ultimately allowed party militants to contest meanings historically attached to the body, sexuality, the political, and everyday life.