In a democracy, the people rule. Citizens exercise power over government by choosing leaders in elections and, on some occasions, expressing their preferences on matters of policy directly. The quality of democracy therefore depends not only on how well leaders and political institutions respond to the needs and desires of the people, but also how effectively citizens participate in the process of self-government. A growing body of evidence testifies to the important role emotions play in shaping the ability and motivation of citizens to take part in politics. Fear, anger, enthusiasm, and other emotions affect public opinion by altering whether and how citizens pay attention, learn, think through their decisions, and act on their opinions. This chapter surveys this new evidence on the emotional foundations of democratic citizenship.