Trump’s supporters exhibit high levels of what political scientists call “authoritarianism.” Authoritarians are unusually fearful of disorder and favor simple, brutal methods of quashing it. As Ezra Klein has noted, “[W]hen many Americans perceived imminent physical threats, the population of authoritarians could seem to swell rapidly.” So by fanning popular fears of chaos, especially violent chaos, Trump wins yet more votes.

He does this, in part, by turning his treatment of the activists who seek to disrupt his events into a parable for how he would restore order in society at large. At a rally in Atlanta last November, an African American man began chanting, “Black Lives Matter.” According to various reports, Trump supporters responded by punching and kicking him while yelling racial slurs. Meanwhile, from the podium, Trump contrasted his response with that of Sanders’s. “You see,” Trump declared, “he was politically correct … I promise you, that’s not going to happen with me. I promise you. Never going to happen. Not going to happen. Can’t let that stuff happen.” Later on Fox News, Trump declared that, “Maybe he should have been roughed up, because it was absolutely disgusting what he was doing.”…

The police are more professional today than they were back then. And video-recording devices are now ubiquitous, which may make such incidents less likely. Then again, Wallace never won a major party’s nomination. Between now and November, Trump could hold hundreds more rallies, many in areas with large African American and Latino populations, in an atmosphere of mounting hysteria as Election Day nears. The young left-wing militants who have already braved danger in places like Ferguson, and who hold their more conflict-averse elders in contempt, are unlikely to stop their disruptions. Trump will keep baiting and threatening them because it’s how he rouses his fans.

How will Americans react if something truly terrible happens? Given the events of recent months, it’s impossible to know.