For those bewildered by why so many Americans apparently voted against the values of liberal democracy, Balint Magyar has a useful formulation. “Liberal democracy,” he says, “offers moral constraints without problem-solving” — a lot of rules, not a lot of change — while “populism offers problem-solving without moral constraints.” Magyar, a scholar of autocracy, isn’t interested in calling Donald Trump a fascist. He sees the president-elect’s appeal in terms of something more primal: “Trump promises that you don’t have to think about other people.” Around the world, populist autocrats have leveraged the thrilling power of that promise to transform their...