This article argues that the low levels of descriptive representation of women in local political office in Mexico and Latin America is much more than a problem of the purported patriarchal cultures of indigenous and rural communities. We claim, based on a comprehensive survey of 466 municipal governments in the indigenous state of Oaxaca, that the underrepresentation of women is a function of institutions limiting female candidates. We test this “candidate supply” hypothesis, adapted from US-based studies, against the hypothesis that culture – as measured by indigenous ethnicity – has an independent effect on women’s representation. We disconfirm that patriarchal, traditionalist cultures of indigenous communities cause underrepresentation in the election of women and instead find that a particular set of local institutions, which are more prevalent in indigenous municipalities, blocks the supply of potential women candidates. We conclude by considering the normative implications for women’s representation in local politics in Mexico and Latin America.