Five years ago next month, British voters, in the largest turnout election ever, voted to leave the European Union by a 4-percentage-point margin. It was an unexpected result and a harbinger of Donald Trump’s even more unexpected election as president five months later.

In both countries, key votes were cast by white non-college graduates. Blue-collar Democrats in Pennsylvania and the Midwest switched to Trump. Working-class voters long loyal to Labour joined leading Conservatives in supporting Brexit.