Classic studies of a few extreme, almost pathological cases of rigidity in political leaders (e.g., Woodrow Wilson's League of Nations debacle) have tended to obscure the fact that virtually all leaders alternate between periods of pragmatic flexibility and rigid intransigence in the face of political opposition or unpleasant facts. This study develops a general theoretical framework for explaining rigidity and flexibility in political leaders by extending insights from classic studies of extreme cases to everyday policymaking and by integrating these findings with more recent theoretical and empirical work in political psychology. The plausibility of hypotheses derived from this framework is investigated by examining the conditions associated with pragmatism and rigidity in 15 cases from the presidency of Ronald Reagan. The results are generally consistent with the proposed model, which stresses person-situation interaction and traces rigidity to the arousal of leaders' sources of self-validation in a particular policy context. I conclude by evaluating the implications of this new framework for other areas of theory and research.