They Loved Taylor Swift. They Loved Football. Then Their Worlds Collided.

Emily Calhoun remembers the moment she realized her worlds were colliding. It was in the early days of the 2023 N.F.L. season, and suddenly her phone was buzzing nonstop.

“Twelve people called me,” she said. “‘Are you seeing this?!’”

Ms. Calhoun, who was raised on Denver Broncos football, sure was. It was impossible to miss the seismic overlap. Her love of football was fusing with her fandom of another pop culture phenomenon: a onetime country singer whom Ms. Calhoun, 38, had come to love in the early 2000s.

We’re talking, of course, about one of the most consequential mergers of our time, one that united two of the world’s most rabid fan bases in unholy internet matrimony: Taylor Swift and the N.F.L., via her boyfriend, Kansas City Chiefs tight end Travis Kelce.

For the sliver of fans like Ms. Calhoun, it’s been a joyful, and complicated, overlap of identities and algorithms. They have been in fantasy drafts and in the Ticketmaster queues. They’re in the same stadiums for the Eras Tour as they are on a Sunday in September. They’re probably even in your football groupchats, the middle section of the Venn diagram that has animated American sports for the last year: Swifties who grew up football die-hards.

“It was like two elemental forces that shouldn’t be allowed to touch,” Prof. Galen Clavio, who studies sports and social media at Indiana University, said of the collision.

In the months since the Swift-Kelce relationship started, a considerable amount of ink has been spilled on the dynamics of their romance. There was the outrage over the pop star supposedly usurping substantial camera time during N.F.L. broadcasts (she really wasn’t), the navel-gazing over whether the relationship was a publicity stunt, and then, finally, the spiral into conspiracy, with some right-wing commenters speculating that the relationship was somehow a scheme to support President Biden in the 2024 election.