The election of President Trump marked significant changes in the content, outlets, and the level of civility of political rhetoric. The traditional left/right policy disagreements took on a more populist tone, activating extremist elements within society. We explore the consequences of political appeals to nationalist identity within the context of modern-day America. We argue that employed by elected officials, nationalist political rhetoric legitimizes extremist views and their expression. This effect is exacerbated by the social media, which provides an unmoderated channel for communication between elected officials and their extremist supporters. We test the link between nationalist rhetoric and hate crimes using data collected from Twitter, as well as an original dataset on daily hate incidents in the US, between February 2017–April 2018, and find strong evidence for our theory. Our results have important implications for the study of political communication and political violence.