Oklahoma Sen. Markwayne Mullin and Teamster President Sean O’Brien were involved in a heated argument on the Senate floor broken up by Sen. Bernie Sanders.

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."

Teamsters boss Sean O'Brien endorses Sen. Markwayne Mullin for DHS chief, two years after their viral Senate hearing nearly turned into a physical fight. (Bill Clark/CQ-Roll Call, Inc via Getty Images; Kevin Dietsch/Getty Images)

"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."

GOP SENATORS TANGLE WITH NOEM DURING HEATED HEARING ON HER HANDLING OF DEPORTATION SURGE

Sens. Bernie Sanders and Markwayne Mullin and Teamster President O'Brien (Reuters // Getty Images)

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.

WATCH: The Teamsters president started it: Sen. Markwayne Mullin

GOP SENATOR BLOCKS TRUMP DHS NOMINEES UNTIL NOEM TESTIFIES BEFORE SENATE

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.

CLICK HERE TO DOWNLOAD THE FOX NEWS APP

Sen. Markwayne Mullins', R-Okla., speaking to reporters shortly after he was nominated to lead DHS.  (Anna Moneymaker/Getty Images)

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. 

Michael Dorgan is a writer for Fox News Digital and Fox Business.

You can send tips to michael.dorgan@fox.com and follow him on Twitter @M_Dorgan.

Get the latest updates from the 2024 campaign trail, exclusive interviews and more Fox News politics content.

By entering your email and clicking the Subscribe button, you agree to the Fox News Privacy Policy and Terms of Use, and
        agree to receive content and promotional communications from Fox News. You understand that you can
        opt-out at any time.

Subscribed

You've successfully subscribed to this newsletter!