Political scientists are increasingly exploring the psychological underpinnings of voting behavior using field experimental techniques. Research in psychology demonstrates that positive reinforcement—what I describe as positive social pressure—motivates prosocial behavior. A distinctive feature of the current study is the focus on key subgroups of voters, namely unmarried women and minorities. Attention to these voter subgroups allows us to build upon findings reported in previous studies that leave questions about the generalizability of the reported effects of positive social pressure to key demographic subgroups of voters largely unanswered. This article reports the results of a large-scale randomized field experiment designed to investigate the impact of positive social pressure on voter turnout. The experiment was conducted during the November 2009 gubernatorial election in New Jersey, and the results suggest positive social pressure mobilizes voters. Moreover, the effects appear to be robust across subgroups of voters, including minorities and unmarried women, and both lower- and higher-propensity voters.