How do modern individuals form a sense of the vast societies in which they live? Social cognition has evolved to make sense of small, intimate social groups, but in complex mass societies, comparable vivid social cues are scarcer. Extant research on political attitudes and behavior has emphasized media and interpersonal networks as key sources of cues. Extending a classical argument, we provide evidence for the importance of an alternative and internal source: imagination. With a focus on social welfare, we collected survey data from two very different democracies, the United States and Denmark, and conducted several studies using explicit, implicit, and behavioral measures. By analyzing the effects of individual differences in imagination, we demonstrate that political cognition relies on vivid, mental simulations that engage evolved social and emotional decision-making mechanisms. It is in the mind's eye that vividness and engagement are added to people's sense of mass politics.