Something snapped in American commentary on Donald Trump in the past week or so. Until now, mainstream media discussions of the leading candidate for the Republican presidential nomination have not spared the billionaire real-estate mogul, pouncing on every vulgar expression of his mendacious, bullying, race-bating, bellicose, ignorant, narcissistic demagogy.Commentators with a historical bent have deployed analogies from the American past: the Know Nothing movement that swept Congress in the lead-up to the Civil War; Huey Long; George Wallace; Joe McCarthy; Ross Perot. But the F-word, fascism, has been sparingly used until now.One of the first occasions, by Jeffrey Tucker in last July’s Newsweek, came under the headline “Is Donald Trump a Fascist?” Mr. Tucker was nevertheless cautious. The core of candidate’s message, he said, was business. Together with nativist jingoism, to be sure. Says whatever comes into his mind, of course. Recklessly anti-establishment, no doubt. Somewhat racist, okay. But Mr. Tucker was optimistic: “The political exotica he represents will not last. It’s a moment in time.”Fast-forward to the past couple of weeks. Mainstream Republicans were sounding the alarm.