Why does party identification motivate citizens to participate in politics? From a theoretical standpoint, it is in a partisan's self-interest to free ride on the efforts of others. Yet, mere identification with a party is enough to motivate many people to overcome this structural hurdle. We theorize that, by virtue of aligning one's self with a party, individuals become more likely to react to their political environment with anger and enthusiasm rather than fear. Anger and enthusiasm are associated with approach and continuation of current behavior, while fear triggers behavior reconsideration. In short, party identification stimulates participation via anger and enthusiasm. On the other hand, fear produces thought but not much action. We find support for our model using data from the American National Election Studies (ANES) and an original laboratory experiment.