We advocate for an experimental approach to the study of personality and politics. In particular, we propose an “interactionist” model of political behavior in which the cognitive and behavioral effects of dispositional variables are qualified by experimentally induced contexts. Our operating assumption is that the political effects of personality do not occur in a contextual vacuum, but instead are magnified by the presence of key precipitating or “activating” features of the political environment. We illustrate the approach with four experimental studies of authoritarianism. Results indicate that the effects of authoritarianism depend critically on the presence of situationally induced threat. More generally, we argue that interactions between personality variables and experimental treatments can lead to valuable insights about when and why personality makes a meaningful contribution to public opinion and political behavior. Finally, we close with a critique of the traditional skepticism toward experimentation in political science, and suggest that external validity is an overrated virtue when the research goal is the development of theory rather than the description of “real-world” phenomena.