You could say that the Trump presidency effectively ended when the polls closed election night or when news outlets called the contest for Joseph R. Biden Jr. four days later. You could say that it ended when the Electoral College voted on Monday to make Mr. Biden the president, or that it will end when Mr. Biden is sworn in on Jan. 20.

But by one measure, the Trump presidency ended in mid-November, when online conservatives went bonkers over a picture of Harry Styles in a dress.

The photo of the British singer on the cover of the December Vogue prompted the YouTube personality Candace Owens to tweet, “Bring back manly men.” To Ben Shapiro, the photo shoot was an assault on the concept of manhood itself: “Anyone who pretends that it is not a referendum on masculinity for men to don floofy dresses is treating you as a full-on idiot.”

What does all this have to do with the president’s impending exit? First, it suggests that other conservatives are retaking the role of Troll-Warrior-in-Chief that Mr. Trump conferred on himself.

But it’s also a reminder that the kind of button-pushing cultural politics that predated him — that in many ways helped make a President Trump possible — will survive his tenure.

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As far back as the early 1970s, the “rural purge” in TV — which eliminated bucolic sitcoms like “Green Acres” to make room for urban ones like “All in the Family” — reinforced the idea that there were different Americas with different, and even competing, popular cultures. This dynamic only spread with cable TV and the internet, which sliced and diced us into a nation of niche demos, sharing a geography but occupying different psychic spaces.

As the historians Kevin M. Kruse and Julian E. Zelizer write in “Fault Lines,” their study of American polarization since the 1970s, all this led to “a world with fewer points of commonality in terms of what people heard or saw.” This was true in politics and in entertainment, and the two often overlapped.

There was now identifiable red and blue pop culture. A 2016 Times study found a TV divide that mirrored the rural-urban split in the election. “Deadliest Catch,” the reality show about Alaskan crab fishing, was popular in red America; in blue zones, “Orange Is the New Black,” the Netflix drama and critique of the prison system.