This article argues that in his “Party Press Essays,” James Madison expounds a psychology of public opinion that is identifiable, but less developed, in his earlier writings. In these essays, Madison explains how a territorial mean, or a “practicable sphere,” contributes to a psychological mean that creates a context for the emergence of an enlightened majority capable of mobilizing against an abusive regime. Attending to Madison’s psychology of public opinion highlights the political importance of affect in Madison’s thought and clarifies his position regarding the appropriate role of the people in a republic.