WASHINGTON — Senate Republicans passed a party-line rebuke Tuesday night of Sen. Elizabeth Warren, D-Mass., for a speech opposing attorney general nominee Jeff Sessions, striking down her words for impugning the Alabama senator’s character.

In an extraordinarily rare move, Majority Leader Mitch McConnell, R-Ky., interrupted Warren’s speech, in a near-empty chamber as debate on Sessions’ nomination heads toward a Wednesday evening vote, and said that she had breached Senate rules by reading past statements against Sessions from figures such as the late senator Edward Kennedy, D-Mass., and the late Coretta Scott King.

“The senator has impugned the motives and conduct of our colleague from Alabama,” McConnell said, then setting up a series of roll-call votes on Warren’s conduct.

It was the latest clash in the increasingly hostile debate over confirming President Donald Trump’s Cabinet, during which Democrats have accused Republicans of trying to force through nominees without proper vetting. Democrats, unable to stop the confirmations that require simple majorities, have countered by using extreme delay tactics that have dragged out the process longer than any in history for a new president’s Cabinet.

The Democratic moves, including boycotting committee room votes on nominees last week and a round-the-clock debate Monday night before Tuesday’s confirmation of Education Secretary Betsy DeVos, reached a boiling point during the debate over Sessions – which Democrats are vowing to continue overnight.

In setting up the votes to rebuke Warren, McConnell specifically cited portions of a letter that King, the widow of slain civil rights leader Martin Luther King Jr., wrote to the Senate Judiciary Committee in opposition to Sessions’ 1986 nomination to be a federal judge.

“Mr. Sessions has used the awesome power of his office to chill the free exercise of the vote by black citizens,” King wrote, referencing controversial prosecutions at the time that Sessions served as the U.S. attorney for Alabama. Earlier, Warren read from the 1986 statement of Kennedy, a senior member of the Judiciary Committee who led the opposition then against Sessions, including the Massachusetts Democrat’s concluding line: “He is, I believe, a disgrace to the Justice Department and he should withdraw his nomination and resign his position.”

The Senate voted, 49 to 43, strictly on party lines, to uphold the ruling that Warren violated rules of debate. Pursuant to those rules, Warren is now forbidden from speaking during the rest of the debate on the nomination of Sessions.

“I am surprised that the words of Coretta Scott King are not suitable for debate in the United States Senate,” Warren said after McConnell’s motion.

Sen. Steve Daines, R-Mont., a freshman who was presiding over the Senate at the time, issued a warning to Warren at that point, singling out Kennedy’s “disgrace” comment, and 25 minutes later McConnell came to the floor and set in motion the battle, citing the comments in the King letter as crossing the line.

Warren’s speech ended with a simple admonition from Daines: “The senator will take her seat.”

Later, McConnell defended his decision.

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

Other Democrats later came to her defense and tried to have King’s letter placed into the Senate record. But Republican senators quickly objected. They did so again when Sen. Kamala Harris, D-Calif., the chamber’s only African-American woman, asked that Warren be allowed to resume participation in the debate.

Warren, a liberal firebrand with a devoted national following whom some activists want to run for president in 2020, quickly took to social media and the airwaves to attack McConnell and Republicans for shutting down her speech.

In a brief telephone interview with MSNBC’s “The Rachel Maddow Show,” a program watched loyally by many Warren devotees, she explained that “I’ve been red-carded on Sen. Sessions, I’m out of the game of the Senate floor. I don’t get to speak at all.”

Public reaction to the Senate floor drama intensified quickly online. RedBubble.com, an online clothing website for independent designers, began selling a “She Persisted” T-shirt or sweatshirt — seizing on McConnell’s admonition of Warren. Democrats began using LetLizSpeak on Twitter and posted copies of King’s letter on Facebook to draw more attention to Warren’s speech.

At least one other Democrat, Sen. Christopher Murphy (Conn.), hinted that he might try to pick up where Warren left off at some point overnight, saying on Twitter, “Go ahead and rule me out of order.”