In what has been an unusually contentious day in Congress, a fistfight nearly broke out between Senator Mullin and the president of the Teamsters union, Sean O’Brien. The latter’s venomous posts on X led Mr. Mullin to stand up for a fight in a committee hearing before Senator Sanders told him to step back. 

“You tweeted at me one, two, three, four, five times,” Mr. Mullin said during a Health, Education, Labor and Pensions Committee hearing, holding up sheets of paper with the posts printed on them. The Oklahoma senator then read the most vitriolic of the messages. 

“Greedy CEO who pretends like he’s self made,” Mr. O’Brien wrote of the senator in June. “In reality, just a clown & fraud. Always has been, always will be. Quit the tough guy act in these Senate hearings. You know where to find me. Anyplace, Anytime cowboy.” Mr. Mullin and his wife founded and own a successful plumbing company in their home state. 

“Sir, this is the time, this is the place,” Mr. Mullin said after reading the message. “If you want to run your mouth, we can be two consenting adults and finish it here,” to which Mr. O’Brien responded, “Okay. That’s fine. Perfect.”

“Stand your butt up, then,” the senator then said. Mr. O’Brien shot back, “You stand your butt up, big guy.”

Mr. Mullin, a professional mixed martial artist, then shot out of his chair at the dais and began to remove his wedding band while beginning to move toward the witness stand. The chairman of the committee, Mr. Sanders, quickly intervened before Mr. Mullin could move any farther. 

“Hold it, hold it, stop it,” Mr. Sanders said, waving his hand in the air. “You’re a United States senator. Sit down, please.”

“This is a hearing,” the Vermonter continued. “God knows the American people have enough contempt for Congress. Let’s not make it worse.”

The senator and the union boss have one of the most famous rivalries in Washington since an extremely contentious exchange between the two men took place earlier this year.

“We weren’t requiring them to pay your guys’ exorbitant salaries,” Mr. Mullin said to Mr. O’Brien in June, speaking about the non-union workers at his small business that were making more than unionized workers doing similar work. “What do you make, Mr. O’Brien?” he asked. 

“You’re out of line,” the Teamsters president said. “I bet I work more hours than you do — twice as many hours. … We hold greedy CEOs like yourself accountable. … You want to attack my salary, I’ll attack yours.”

The House was not doing much better as of Tuesday. Before the close of business, a former speaker, Congressman Kevin McCarthy, reportedly shoved one of the eight members who voted to remove him from office, Congressman Tim Burchett.