This paper examines whether and how electoral rules moderate the effect of voter bias on candidate choice. Voter bias against female candidates follows a pattern known as aversive sexism, which denotes that voters discriminate when the choice structure does not make the bias clear to others and to themselves. As a result, voters are less likely to vote for women when they can substitute ideologically close female candidates with male co-partisans. The paper uses survey data and a ballot experiment in Brazil to investigate why, contrary to conventional wisdom on the topic, voters are more likely to elect women running in plurality races for the Senate than in proportional races for the Chamber of Deputies. The results shed light on how institutions can produce voting patterns that harm the electoral prospects of female candidates.