In this paper, we argue that a stable set of characteristics—personality—can help explain mass political opinions and behavior. By analyzing data collected from over 750 people, we examine the influence of the Five-Factor Model of personality on ideology, partisanship, political efficacy, and two forms of political participation. After controlling for a host of demographic factors, we find that openness to experience, agreeableness, conscientiousness, and extraversion help explain public opinion and political behavior. Neuroticism is the only factor that does not influence political life. We conclude by comparing these results to other findings in the field and suggest directions for future research.