The Democratic establishment, shaken by the rise of progressive socialists, is right to wonder where this wave might lead. The similarly populist movement of Tea Party Republicans, however muddled, foreshadowed President Donald Trump. Republican candidates for Congress backed by the GOP establishment were pushed to the limit beginning in the 2010 election cycle and continuing through 2012 and 2014. Some even fell in key primaries to conservative populists who identified as Tea Party candidates.