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The lesson of the Brexit: Take Donald Trump very seriously.

That Trump is in Scotland today can be read as nothing other than a screaming warning from the gods. The Brexit was animated by several forces—nostalgia for British greatness, the very real failures of the European Union—but underlying it all was anti-immigrant sentiment. This became increasingly explicit as the campaign to “Leave” entered the home stretch, punctuated by the killing of Labour MP Jo Cox. If we define Trumpism as a resurgence of ethno-nationalism in response to a perceived weakening of cultural identity brought on by immigration and globalization, then Brexit is proof that Trumpism is a global phenomenon. Trump has drawn the comparison himself, saying, “I think there are great similarities between happened here and my campaign. People want to take their country back.”

There is a tendency among political and media elites to dismiss such phenomena. There is an ingrained belief that cooler heads will ultimately prevail, that voters will do “the right thing,” that things will be as they were before. David Cameron certainly believed this, blithely betting his country’s future to win an election. It might be facile to assert that if British voters could vote to leave the European Union, then American voters could vote to put Trump in the Oval Office. But the Brexit is shocking evidence that you can’t be too sure.