Nearly two and a half years after they nearly came to blows in a viral Senate hearing, Teamsters President Sean O’Brien offered praise for Sen. Markwayne Mullin, R-Okla., on Thursday after President Donald Trump nominated him to lead the Department of Homeland Security.

"If anyone is willing to stand their butt up to protect America, it’s Markwayne Mullin," O’Brien said in a statement.

The endorsement marked a striking turn for the two men, who clashed publicly in November 2023 during a heated Senate Health, Education, Labor and Pensions Committee hearing that appeared to be on the brink of a physical altercation.

During the exchange, Mullin, a former mixed martial arts fighter, referenced a social media post in which O’Brien had said he could take the senator "any time" or "any place."

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"Sir, this is a time, this is a place. You want to run your mouth, we can be two consenting adults, and we can finish it here," Mullin said at the hearing.

Mullin then stood up and appeared ready to approach O’Brien before then-Committee Chairman Sen. Bernie Sanders, I-Vt., intervened.

"Stop it, hold it, no, no, sit down," Sanders said. "You're a United States senator. Sit down."

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The confrontation continued verbally for several minutes, with Mullin calling O’Brien a "thug" and O’Brien labeling the senator "disrespectful," before Sanders banged his gavel and moved the hearing forward.

The two men had also sparred months earlier over O’Brien’s salary compared to that of union members, forcing Sanders to step in during that hearing as well.

O’Brien’s statement Thursday signaled a sharp contrast from the combative exchanges that once defined their relationship.

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The statement came as Mullin was nominated to lead DHS following what Trump described as a turbulent tenure under current Secretary Kristi Noem, who will be reassigned as Special Envoy for the Shield of the Americas, a new security initiative focused on the Western Hemisphere.

The clash between the two men in November 2023 followed months of escalating tensions, including a public challenge earlier that year when Mullin accepted O’Brien’s social media dare of "anyplace, anytime" and proposed a charitable mixed martial arts fight in Tulsa. But tensions appeared to cool in 2024 after Trump helped broker a truce between the two men.

Mullin later recounted on "Fox Across America with Jimmy Failla" that Trump reached out early to O’Brien as Teamsters members increasingly leaned Republican.

Mullin said O’Brien told him many of his members were backing Trump and that the union boss felt compelled to reflect where "my brothers" stood politically.

Fox News's Andrew Mark Miller and Houston Keene contributed to this report.