Updated 10:22 p.m. | Senate Majority Leader Mitch McConnell and liberal firebrand Sen. Elizabeth Warren clashed on the chamber floor Tuesday evening, with the Kentucky Republican moving for the Massachusetts Democrat to take her seat.

Senators voted along party lines, 49-43, to uphold a ruling of the chair, blocking Warren from speaking for the remainder of the debate on confirmation of fellow Sen. Jeff Sessions as attorney general.

The scene pitted a Trump ally and the Senate Republican leader against a potential 2020 Democratic contender for the White House. Warren backers quickly began using the hashtag #LetLizSpeak to show their support on Twitter.

McConnell objected to Warren’s request that she be allowed to continue her critical remarks about the Alabama Republican, President Donald Trump’s pick to head the Justice Department.

McConnell said Warren had impugned Sessions in contravention of Rule XIX. Warren lost an appeal on a roll call vote, to which Democrats responded with further procedural motions.

“Sen. Warren was giving a lengthy speech. She had appeared to violate the rule. She was warned. She was given an explanation,” McConnell said. “Nevertheless, she persisted.”

Video of Warren and McConnell Sparring Over Coretta Scott King Letter

Montana Republican Sen. Steve Daines, presiding over the Senate, had issued the warning to Warren about impugning Sessions’ motives.

Warren responded by saying that she was merely quoting from materials, including comments by the late Sen. Edward M. Kennedy and a letter from Coretta Scott King regarding Sessions’ earlier nomination to the federal bench in 1986.

Eventually, it was explained that Warren was warned for the quote from Kennedy’s remarks to the Senate Judiciary Committee during consideration of Sessions’ ill-fated nomination for a federal judgeship. In those comments, Kennedy said, “He is, I believe, a disgrace to the Justice Department.”

The ultimate rebuke by McConnell came in response to Warren’s quoting from the King letter. Impugning the motivations of a fellow senator is a violation of the rules of the Senate.

Not long before McConnell came to the floor, Warren had an exchange with Daines.

“The senator is reminded that it is a violation of Rule XIX of the Standing Rules of the Senate to impute to another senator or senators any conduct or motive unworthy or becoming [of] a senator,” Daines said, reading from prepared notes.

“I don’t think I quite understand. I’m reading a letter from Coretta Scott King to the Judiciary Committee from 1986 that was admitted into the record. I’m simply reading what she wrote about what the nomination of Jeff Sessions to be a federal court judge meant,” Warren said.

After the initial vote, Maine independent Sen Angus King made an inquiry of the presiding officer about whether accusing another senator of telling a lie would constitute a violation of the rule under debate Tuesday evening. South Dakota Republican Sen. Mike Rounds, as the presiding officer, suggested that it would.

That was a thinly veiled reference to a 2015 incident when Sen. Ted Cruz accused McConnell of not telling the truth. The Texas Republican was absent from the Tuesday evening’s proceedings, debating Vermont independent Sen. Bernie Sanders on CNN.

Later in the debate, Rounds was pressed by Democratic Sen. Sheldon Whitehouse of Rhode Island to explain that a statement cannot be made against another senator, even if the statement is truthful. Unlike with traditional libel and slander cases, truth is deemed no defense by the Senate.

John T. Bennett contributed to this report.

Senate Democrats Reading Coretta Scott King’s Letter Opposing Sessions