When Argentine president Mauricio Macri announced in March 2018 that he supported a “responsible and mature” national debate regarding the decriminalization of abortion, it took many by surprise. In a Catholic country with a center-right government, where public opinion regarding abortion had hardly moved in decades—why would the abortion debate surface in Argentina when it did? Our answer is grounded in the social movements literature, as we argue that the organizational framework necessary for growing the decriminalization movement had already been built by an emergent feminist movement of unprecedented scope and influence: Ni Una Menos. By expanding the movement's social justice frame from gender violence to encompass abortion rights, feminist activists were able to change public opinion and expand the scope of debate, making salient an issue that had long been politically untouchable. We marshal evidence from multiple surveys carried out before, during, and after the abortion debate and in-depth interviews to shed light on the sources of abortion rights movements in unlikely contexts.