In recent years, scholars have been very interested in the role of sexism in U.S. politics. An array of different measures of sexism have been used in empirical studies, but none have explored sexism with regard to political leadership in particular. Building on the literature on gender stereotypes, this paper introduces a new measure of sexism, leadership sexism, that focuses on differences between perceptions of men and women in terms of personality traits that people routinely use to evaluate political candidates. National survey data demonstrate that leadership sexism taps a type of sexism distinct from commonly used measures. Moreover, leadership sexism predicts vote choice in the 2016 and 2020 U.S. presidential elections, whereas other measures of sexism do not. Thus, leadership sexism appears to be a useful addition to scholars' toolbox for understanding the role of attitudes toward women in shaping American politics.