The 2016 presidential election represents the latest chapter in the disintegration of the legacy institutions that had set bounds for U.S. politics in the postwar era. It is tempting (and in many ways correct) to view the Donald Trump campaign as unprecedented in its breaking of established norms of politics. Yet this type of campaign could only be successful because established institutions—especially the mainstream media and political-party organizations—had already lost most of their power, both in the United States and around the world. The void that these eroding institutions left was filled by an unmediated populist nationalism tailor-made for the Internet age.