Despite the inroads women have made in American politics in recent decades, women still hold far fewer elective offices than men. This raises the question of why women fall short in this important mode of political engagement. Early research on this question emphasized the obstacles created by gender socialization, women's underrepresentation in the professions most likely to produce candidates, and women's family and household responsibilities. Scholars have also found that some voters use gender stereotypes in evaluating candidates. Importantly, however, the average female candidate wins the same percentage of the vote as the average male candidate, and that fact has become the basis for the widespread belief that voters are not systematically biased against female candidates—that the cause of women's underrepresentation must lie elsewhere. Cutting-edge political science research has found that women are less likely than men to even consider running for office, that recruiters prefer to recruit male candidates over female candidates, and that primary races that feature female candidates attract larger numbers of challengers than all-male primary races. But other cutting-edge work suggests that the widely accepted conclusion that voters harbor no bias against female candidates is likely incorrect. Future research will likely reevaluate this conclusion using new approaches and methods and will also delve deeper into the question of why women are less politically ambitious than men. These lines of inquiry will likely borrow insights from psychology, sociology, and economics, as well as the political science literature on race.