Wishful thinking is a useful reflex against fear. When Donald Trump started to rise in the opinion polls, I told myself that his partisans wanted to send an angry message to the ruling elites but that surely they wouldn't want to see him in the Oval Office and that they would soon opt for a serious contender.
When he went on to lead in the state caucuses and primaries, I told myself that, even if he became the Republican nominee, Hillary Clinton would beat him hands down. Considering that Mr. Trump is arguably the craziest of the Republican contenders, I again told myself, wouldn't it make Ms. Clinton's victory easier than if she were facing a moderate, credible adversary?
Now I'm not so sure. All the Republican moderates have been, or will soon be, eliminated. The last man standing against Mr. Trump might be Texas Senator Ted Cruz, who in his way is even scarier than Mr. Trump because he is a dogmatic social conservative, a puritan hawk whose political agenda has been written by God himself. And there is a remote possibility that Ms. Clinton, even though she is sailing toward the nomination, could be defeated by a forceful Republican who crosses party lines and is the ultimate "outsider" – namely, Mr. Trump.
This would be in tune with the current populist climate, where masses of people are rebelling against the traditional political class. And Ms. Clinton, the ultimate "insider," is vulnerable. Otherwise, she wouldn't have lost eight primaries and caucuses to a relatively marginal senator, a self-described socialist, on whom nobody would have bet a five-dollar bill a year ago.
The surprising rise of Vermont Senator Bernie Sanders in the polls and the enthusiasm he generates are not only signs that millions of Americans are moving more toward the left, but also are an indirect rejection of Ms. Clinton – her greedy ties to Wall Street, where corporate speaking fees made her a multimillionaire in the runup to her official candidacy; her mediocre performance as secretary of state; her use of her private e-mail in communicating with the administration, a scandal that could theoretically prevent her from running for office. Worse, given that perceptions are everything in politics, people don't seem to be attracted to her emotionally. She is seen as cold, calculating, scripted – a big contrast with Mr. Trump, who exudes self-confidence and spontaneity and likes to give the impression of telling the truth.
Some pundits have likened him to Hitler, which is silly. The only historical character he might evoke would be Mussolini: As with the fascist Italian dictator, who started as a labour union leader, part of Mr. Trump's agenda comes from the left (his rejection of free trade, his approval of publicly funded health care), and on most issues he doesn't come across as a social conservative. He is, like Il Duce, a staunch authoritarian, and if he were in a country without the admirable U.S. system of checks and balances, he might become a kind of dictator.
More to the point, he is a xenophobic populist leader – a growing breed in Britain, France, Poland, Croatia, Hungary, Slovakia and even Scandinavia. One difference is that Mr. Trump is more vulgar and more ignorant than his European counterparts. But – and this is the appalling difference – the United States isn't just any country. What happens there will affect the whole world.