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Although UFC president Dana White is a Trump supporter, the sport featuring many Latino, African American and immigrant fighters isn't naturally friendly political turf for the president. Perhaps reflecting its large Latino fan base, Mexican beer Modelo last year replaced Bud Light as the organization's official brew.
Trump attended the event with sons Donald Jr. and Eric, as well as a group of congressional Republicans, including House Minority Leader Kevin McCarthy of California, Mark Meadows of North Carolina and Peter King of New York.
Some MMA fans held signs reading "Remove Trump" and "impeach Trump."
Later, Donald Trump Jr. tweeted that his father's reception was "overwhelmingly positive."
"@danawhite said it was the most electrifying entrance he seen in 25 years of doing this," he tweeted.
Several dozen demonstrators, including members of local anti-fascist groups, gathered outside the venue in Midtown Manhattan to protest Trump's visit, some holding placards that read "Impeach Trump" and chanting "Out now!"
The president's late nemesis, Sen. John McCain, R-Arizona, was an early critic of mixed martial arts and, in 1996, at a time when the sport was sometimes staged in seedy bars, famously described it as "human cockfighting."
Trump hosted boxing at his defunct Atlantic City venues, and he was inducted into the WWE Hall of Fame in 2013 after participating in occasional pro wrestling side shows. Recently, he's become a friend of the Las Vegas-based UFC, and White endorsed him for president in 2016.
In the main event Saturday between welterweights Nate Diaz and Jorge Masvidal, a technical knockout was called in the third round in favor of Masvidal because a doctor was concerned about a cut on Diaz's face.
Dennis Romero writes for NBC News and is based in Los Angeles.