When it comes to politics, people care what other people think. Although a familiar phenomenon, existing theories of public opinion poorly understand the psychological underpinnings of this impulse. Here, I draw on cross-disciplinary findings that highlight the distinctiveness of human moral psychology and examine the role it plays in politics. In three stand-alone chapters that use an array of survey and experimental data, I find that citizens’ intuitions about morality profoundly influence how they respond to political disagreement, their acceptance of political compromise, and how they process political information.The first paper, ;;Reconsidering Moral Issues in Politics,” challenges the conventional claim that moral and economic issues are natural kinds, fundamentally distinct in the mind of the average citizen. Instead, I show that some citizens ;;moralize” economic issues, and that the psychological patterns typical of morality—e.g. growing angry at disagreement—arise on economic and noneconomic issues alike.The second paper, ;;No Compromise: Political Consequences of Moralized Attitudes,” examines the relationship between moral conviction and approval of political compromise. I find that attitudes can be intense in ways that permit compromise, but that morally convicted attitudes orient citizens to oppose compromises and punish compromising politicians. One study in ;;No Compromise” shows that citizens with morally convicted attitudes eschew even concrete monetary benefits to prevent a disliked group from gaining.The third paper, ;;Unthinkable! How Citizens with Moralized Attitudes Process Political Arguments,” identifies a connection between moral psychology and patterns discussed under the heading of ;;motivated reasoning.” I find that many citizens are responsive to political information that challenges their existing attitudes, but that citizens with morally convicted attitudes are particularly resistant to disconfirming information. As such, I argue moral psychology represents one chief mechanism by which motivated reasoning operates.This research demonstrates that taking account of different aspects of attitude intensity enriches the scholarly understanding of how citizens interact with the political environment—with moral conviction playing a powerful role. It invites future research on what causes moral convictions to take hold and the extent to which political elites can galvanize or stifle their effects.