Last weekend, Mr. Trump attended Game 5 of the World Series at Nationals Park in Washington, where he was vigorously booed. Chants of “lock him up!” rang around the stadium — a twist of the oft-evoked Trump rally chant of “lock her up!” aimed at his 2016 election opponent Hillary Clinton.
On Saturday, as Mr. Trump’s motorcade approached the Garden, one onlooker held a sign that read “headlock him up.”
The headlining event was a fight between Nate Diaz, the U.F.C.’s most unpredictable star, and Jorge Masvidal, a Trump supporter. The card of a dozen bouts was built mainly around glitz and drama, not an actual championship with the only belt at stake a profanely-named title to declare the “baddest” fighter between Mr. Diaz and Mr. Masvidal.
Still, it is expected to be one of the biggest U.F.C. pay-per-view events of the year, magnified by the presence of Mr. Trump as well as Dwayne Johnson, the star actor who once wrestled as the Rock and was expected to award the main event winner the specially-created belt.
“Hey, the president is showing up to my fight,” Mr. Masvidal told TMZ recently. “So that’s humbling in itself.”
Mr. Trump has been associated with the U.F.C. for almost 20 years. Mixed martial arts faced an uncertain future in the early 2000s after Senator John McCain, describing it as “human cockfighting,” led a charge to ban the sport, which is regulated state by state. Mr. Trump agreed to host a number of fights at the Trump Taj Mahal in Atlantic City, giving the U.F.C. a lifeline.
“I’m never going to say anything bad about Donald Trump, ever,” Dana White, the U.F.C. president, told Fox News last year. “Ever, ever, ever. That guy gave us our start when nobody would talk to us.”