I went to see Roger Goodell at the N.F.L.’s headquarters at 345 Park Avenue, the morning after a sluggish docket of first-round playoff games in early January. The commissioner was sitting in his sixth-floor office, sipping water and battling a cold. Goodell, who is 58, wore a beige V-neck sweater and looked somewhat worn down but freshly worked-out; he had just come from a Pilates class at a studio not far from the office. It had been a “challenging” season, Goodell allowed — there are never “problems,” only “challenges” for this commissioner — but every season has its issues. “Never has there been a period in our history where everything’s been great,” he said. “We’ve always had our challenges.”

Goodell, the son of the former Republican senator from New York Charles Goodell, is a gifted political animal. He can come off as stiff and cautious in speeches and on TV — and can in fact be stiff and cautious in person too — but he was also clearly bred for public life, and adept at turning it on as necessary. He is a prodigious slapper of backs, squeezer of shoulders and knower of names. He laughs easily — maybe for real, or maybe not. He has also mastered the paramount political skill of prioritizing constituencies, none more so than the 32 N.F.L. team owners who employ him, the “membership,” as they are known to one another. “You have to be able to deal with and get along with 32 different personalities,” John Mara, the president and an owner of the New York Giants, told me. “We range from people like me who were born in a family business, and people who are self-made billionaires who think they know everything about everything.”

Then there was that other billionaire — the one in the White House. From early in his presidential campaign, Donald Trump held up the N.F.L. as a symbol of the sissified and hypersensitive culture he was running against: “You used to see these tackles, and it was incredible to watch, right?” Trump said at a campaign rally in Nevada in early 2016. “But football has become soft like our country has become soft.”

Culture-war critiques of the N.F.L. were previously mostly confined to the left. Liberals were far more prone to suspicion of football for its violence, militaristic sensibility and over-the-top displays of patriotism. But Trump struck a throbbing nerve on the right, making the N.F.L. an improbable symbol of permissive leadership and political correctness.

Seven months after Trump’s Nevada rally, and just in time for the general election, Colin Kaepernick, the quarterback for the San Francisco 49ers, took to kneeling during the national anthem before preseason games: a protest, he explained, against police brutality endured by African-Americans and other minorities. It was only a matter of time before Trump served up the vegan Kaepernick as red meat to his base. “The N.F.L. is way down in their ratings,” Trump taunted the league at a campaign rally in Greeley, Colo., a week before the election. He said that politics was “a much rougher game than football” and also more exciting. “We’ve taken a lot of people away from the N.F.L.,” Trump boasted. “And the other reason is Kaepernick — Kaepernick!”

Well before Kaepernick was even born, the N.F.L. had figured prominently in the future president’s personal ledger of grievance and unreturned affection. Trump had wanted into the membership for years, even though his earlier foray into football — as the owner of the short-lived United States Football League’s New Jersey Generals in the 1980s — ended disastrously, with the league’s collapse. In 1984, he finagled himself a meeting with the N.F.L. commissioner at the time, Pete Rozelle, at the Pierre Hotel in New York, in which he told Rozelle he would do whatever it took to get himself into the league, according to an account of the meeting in “Football for a Buck,” the sportswriter Jeff Pearlman’s coming book on the U.S.F.L. Rozelle was not impressed.

Rozelle was Goodell’s mentor and idol, almost from the day Goodell set foot at the league in 1982. Rozelle’s dim view of Trump — whom he saw as a clown and a con man — trickled down to his protégé, though Goodell is careful never to share his views on Trump publicly. He has met Trump at least twice over the years, once at a Yankees game about 15 years ago and then a few years later at a small dinner gathering. Goodell found Trump to be pleasant, engaging and solicitous in those limited encounters — maybe because Trump was still, at the time, angling for a place in the membership. In 2014, he tried to buy the Buffalo Bills, only to have his bid passed over. After losing out on Buffalo, Trump lashed out at his owner friends — particularly New England’s Robert Kraft — for not doing more to grease his entry into the league. He also told friends that the N.F.L., particularly Goodell, was intent on freezing him out, on account of his history with the U.S.F.L.