The junior senator of Oklahoma, Markwayne Mullin, is challenging the Teamsters president, Sean O’Brien, to a cage match after a dispute between the two erupted on social media.

Mr. Mullin on Monday tweeted a response to a tweet from Mr. O’Brien in which he said that Mr. Mullin is a “clown and fraud” and vowed to fight him “Anyplace, Anytime, cowboy.”

“Greedy CEO who pretends like he’s self made,” Mr. O’Brien, a famously combative figure who took over as president of the Teamsters last year, said. “Quit the tough guy act in these senate hearings. You know where to find me.”

In response, Mr. Mullin said Mr. O’Brien is an “attention-seeking union Teamster boss” who “is trying to be punchy after our Senate hearing.”

“Okay, I accept your challenge. MMA fight for charity of our choice. Sept 30th in Tulsa, Oklahoma,” Mr. Mullin said. “I’ll give you three days to accept.”

The challenge between Messrs. Mullin and O’Brien echoes the cage match challenge from billionaire Elon Musk to billionaire Mark Zuckerberg last week, which also played out over social media.

Although Mr. Musk eventually backed off from his challenge after images of Mr. Zuckerberg training in Jiu Jitsu began circulating, the interaction may have sparked a trend. 

The latest challenge is the culmination of a feud that began during a March Senate hearing in which Mr. O’Brien called Mr. Mullin a “greedy CEO” before Mr. Mullin told Mr. O’Brien, “Sir, you need to shut your mouth.”

In a statement issued to Fox News following the hearing, Mr. Mullin took the opportunity to go after unions as well as Senator Sanders, chairman of the Senate Health, Education, Labor and Pensions Committee, which held the hearing.

“The behavior we saw today was typical of how union bosses, many of whom have never created a single job, use intimidation tactics to pressure employees into joining unions which some workers may deem to be against their interests,” Mr. Mullin said.

Mr. O’Brien also went after Mr. Mullin publicly following the hearing, asking, “What have you done for working people” in Oklahoma? 

“Last time I checked, your state ranks near the bottom in median wages,” Mr. O’Brien said. “Sounds like you need to shut your mouth and get to work for the people of your state. They deserve action, not your phony ‘man of the people’ spiel.”

After a lengthy back and forth with plenty of name-calling and an occasional expletive, Mr. Mullin’s office released a press release saying that the senator was ready to fight to benefit charity.

“In short, 15 years after retiring from MMA, Senator Mullin is coming out of retirement to raise money for charity on a Saturday afternoon in Tulsa this coming September,” the press release reads.

Mr. O’Brien did not immediately respond to a request for comment.