The fulminations surrounding the world’s biggest pop icon — and girlfriend of Chiefs tight end Travis Kelce — reached the stratosphere after Kansas City made it to the Super Bowl.

For football fans eager to see a new team in the Super Bowl, the conference championship games on Sunday that sent the Kansas City Chiefs and San Francisco 49ers back to the main event of American sports culture were sorely disappointing.

But one thing is new: Taylor Swift. And she is driving the movement behind Donald Trump bonkers.

The fulminations surrounding the world’s biggest pop icon — and girlfriend of Travis Kelce, the Chiefs’ star tight end — reached the stratosphere after Kansas City made it to the Super Bowl for the fourth time in five years, and the first time since Ms. Swift joined the team’s entourage.

The conspiracy theories coming out of the Make America Great Again contingent were already legion: that Ms. Swift is a secret agent of the Pentagon; that she is bolstering her fan base in preparation for her endorsement of President Biden’s re-election; or that she and Mr. Kelce are a contrived couple, assembled to boost the N.F.L. or Covid vaccines or Democrats or whatever.

“I wonder who’s going to win the Super Bowl next month,” Vivek Ramaswamy, the conspiratorial presidential candidate, turned Trump surrogate, pondered on social media on Monday. “And I wonder if there’s a major presidential endorsement coming from an artificially culturally propped-up couple this fall.”

The pro-Trump broadcaster Mike Crispi led off on Sunday by claiming that the National Football League is “rigged” in order to spread “Democrat propaganda”: “Calling it now: KC wins, goes to Super Bowl, Swift comes out at the halftime show and ‘endorses’ Joe Biden with Kelce at midfield.”

Other detractors of Ms. Swift among Mr. Trump’s biggest fans include one of his lawyers, Alina Habba, one of his biggest conspiracy theorists, Jack Posobiec, and other MAGA luminaries like Laura Loomer and Charlie Kirk, who leads a pro-Trump youth organization, Turning Point USA.

The right has been fuming about Ms. Swift since September, when she urged her fans on Instagram to register to vote, and the online outfit Vote.org reported a surge of 35,000 registrations in response. Ms. Swift had embarked on a world tour that helped make her a billionaire. Gavin Newsom, the California governor, praised her as “profoundly powerful.” And then Time magazine made her Person of the Year in December, kicking off another round of MAGA indignation.

The love story that linked her world with the N.F.L. has proved incendiary. Mr. Kelce’s advertisements promoting Pfizer’s Covid vaccine and Bud Light — already a target of outrage from the right over a social media promotion with a transgender influencer, Dylan Mulvaney — added fuel to that raging fire.

The N.F.L.’s fan base is huge and diverse, but it includes a profoundly conservative element that cheered on the star quarterback Aaron Rodgers’s one-man crusade against Covid vaccines and jeered Black players who knelt during the national anthem. The league has long battled charges of misogyny, from the front offices of the Washington Commanders to multiple cases of sexual and domestic assault and abuse.

The Swift-Kelce story line, for some, has delivered a bruising hit to traditional gender norms, with a rich, powerful woman elevating a successful football player to a new level of fame.

Some of the Monday morning quarterbacking has been downright silly, including speculation that Ms. Swift is after Mr. Kelce for his money. (Her net worth exceeds $1 billion, a different universe than the athlete’s merely wealthy status.)

Other accusations appear to be driven by fear and grounded in some truth, or at least in her command of her 279 million Instagram followers: that she has enormous influence, and has supported Democrats in the past. For much of her extensive music career, Ms. Swift avoided politics, but in 2018, she endorsed two Democrats in Tennessee, where she owns two homes: former Gov. Phil Bredesen, who was running for the Senate against then-Representative Marsha Blackburn, and Jim Cooper, a House member who has since retired.

“I always have and always will cast my vote based on which candidate will protect and fight for the human rights I believe we all deserve in this country,” she wrote on social media. “I believe in the fight for L.G.B.T.Q. rights, and that any form of discrimination based on sexual orientation or gender is WRONG.”

She added, “I believe that the systemic racism we still see in this country towards people of color is terrifying, sickening and prevalent.”

The alarm bells were loud enough to pull Mr. Trump into loudly backing Ms. Blackburn: “I’m sure Taylor Swift doesn’t know anything about her,” he said at the time, knowing all too well how influential Ms. Swift could be. “Let’s say that I like Taylor’s music about 25 percent less now, OK?”

He probably liked her even less in 2020 when she criticized his pandemic response, and then endorsed Mr. Biden.

While her early pop music may have mainly attracted teens and preteens, those fans have reached voting age, and her music has grown more sophisticated with the albums “Evermore” and “Folklore” to match her millennial roots and her fans’ taste.

Much of the Swift paranoia has lurked on the MAGA fringes, with people like Ms. Loomer, the conspiracy theorist from Florida who declared in December that “2024 will be MAGA vs Swifties” and Mr. Kirk, who declared in November that Ms. Swift would “come out for the presidential election” after Democrats had another strong showing in an election that demonstrated the issue of abortion motivated voters to the polls.

“All the Swifties want is swift abortion,” he said.

Then Swift-bashing reached Fox News in mid-January. The host Jesse Watters suggested the superstar was a Defense Department asset engaging in psychological warfare. He tied Ms. Swift’s political voice with her boyfriend’s Pfizer endorsement to the remarkable success of her Eras tour, which bolstered local economies and landed her on the cover of Time.

“Have you ever wondered why or how she blew up like this?” Mr. Watters wondered on air. “Well, around four years ago, the Pentagon psychological operations unit floated turning Taylor Swift into an asset during a NATO meeting.”

Andrea Hailey, the chief executive of Vote.org, made the most of the Fox News criticism, saying the organization’s partnership with Ms. Swift “is helping all Americans make their voices heard at the ballot box,” adding that the star is “not a psy-op or a Pentagon asset.”

But her appearance on the field with Mr. Kelce in Baltimore after the Chiefs beat the Ravens on Sunday, complete with a kiss and a hug, appears to have sent conservatives into a fit of apoplexy that may only grow in the run-up to Super Bowl LVIII in Las Vegas Feb. 11.

The feelings are so strong that Fox News ran a segment on Sunday lamenting that Ms. Swift’s private “jet belches tons of CO2 emissions,” showing a sudden awareness of the leading cause of global warming.

Mr. Ramaswamy said his Super Bowl conjecture was dead serious.

“What your kind of people call ‘conspiracy theories,’ I simply call an amalgam of collective incentives hiding in plain sight,” he said.

The White House press secretary Karine Jean-Pierre stoked speculation still more by invoking the Hatch Act, which prohibits political actions by civil servants, in declining to answer whether Mr. Biden would be appearing with Ms. Swift.

“I’m just going to leave it there,” she said Monday. “I’m not going to get into the president’s schedule at all from here, as it relates to the 2024 elections.”

The Trump campaign, which had initially planned to ignore the frenzy, dispatched Karoline Leavitt, a campaign spokeswoman, to dismiss concerns about a potential Biden endorsement.

“I don’t think this endorsement will save him from the calamity” of his record, she said.