Has Trump granted Americans license to express overt racism or new levels of acrimony? “It seems like a plausible narrative, but I seem to recall all kinds of sketchy things said about races and genders and groups aired publicly on a weekly basis before, say, the summer of 2015,” said John McWhorter, a Columbia University professor who studies public rhetoric. “He is distinct only in being someone of such prominence saying such things. I think the real change was Facebook and Twitter in 2009. Trump is just a symptom.”

Even as offensive language and ethnic insults became routine at Trump rallies, McWhorter saw the real culprit as social media. Twitter and Facebook became the foundations of daily communication for many Americans between 2007 and 2009, “revolutionizing conversation about, well, everything,” and pushing political chatter in a far meaner direction, McWhorter said.

In this view, the Trump effect is not unique to the man, but is a natural, almost inevitable result of economic and social forces unleashed by swift, powerful technological change that had, even before Trump’s candidacy, made the country meaner, more confrontational and more divided.

The populism Trump represents and the social strains that made millions of Americans eager for someone like him appear regularly throughout American history. Previous bursts of populism have usually burned through in less than a generation, fading away as economic expansion, war or political reform eased people’s sense of insecurity.