Although anecdotal stories of political anger and enthusiasm appear to be provoked largely by issues such as gay marriage or healthcare reform, social sorting is capable of playing a powerful role in driving anger and enthusiasm, undercutting the perception that only practical disagreements are driving higher levels of political rancor. Because a highly aligned set of social identities increases an individual’s perceived differences between groups, the emotions that result from group conflict are likely to be heightened among well-sorted partisans. An experimental design in a national online survey manipulates political threats and reassurances, including a threat to a party and a threat to distinct policy goals. Issue positions are found to drive anger and enthusiasm in the presence of issue-based messages, but not all party-based messages. Partisan identity drives anger and enthusiasm in the presence of party-based threats and reassurances, but not all issue-based messages. Social sorting, however, drives anger and enthusiasm in response to all threats and reassurances, suggesting that well-sorted partisans are more reliably emotionally reactive to political messages. Finally, these results are driven not by the most-sorted partisans, but by the emotional dampening effect that occurs among those with the most cross-cutting identities. As social sorting increases in the American electorate, the cooler heads inspired by cross-cutting identities are likely to be taking up a smaller portion of the electorate.