Influencing the lawmaking process is crucial for social movement success, but activists struggle to specify the content of bills. This article proposes that activists can shape legislation through strategic defeat, which involves using tactics expected to fail in achieving their primary goal but aimed at securing alternative advantages to enhance the movement's position. To develop this concept, this study draws on archival research and interviews with LGBT+ leaders, legislators, and key informants who participated in the campaign to legalize civil unions in Chile, where activists introduced politically unfeasible bills. While this strategic choice seems counterintuitive, their aim was not to pass these bills but to gain access to legislative spaces and cultivate a network of supporters. Then, as political conditions improved, activists leveraged these advantages to significantly shape the civil unions law. This article highlights how specialized strategic choices create opportunities for influence and reevaluates the role of defeat for social movements.