U.S. historical accounts of partisanship recognize its contentiousness and its inherent, latent threat of violence, but social scientific conceptions of partisan identity developed in quiescent times have largely missed that dangerous dimension. We rebalance scholarly accounts by investigating the national prevalence and correlates of 1) partisan moral disengagement that rationalizes harm against opponents, 2) partisan schadenfreude in response to deaths and injuries of political opponents, and 3) explicit support for partisan violence. In two nationally representative surveys, we find large portions of partisans embrace partisan moral disengagement (10-60%) but only small minorities report feeling partisan schadenfreude or endorse partisan violence (515%). Party identity strength and trait aggression consistently increase each kind of extreme party view. Finally, experimental evidence shows inducing expectations of electoral victory give strong partisans more confidence to endorse violence against their partisan opponents. We conclude with reflections on the risks of lethal partisanship in democratic politics, even as parties continue to serve as essential bedrocks of democracy.