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 M. 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 continued 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 Rule 19 of the Senate that says senators are not allowed to "directly or indirectly, by any form of words impute to another Senator or to other Senators any conduct or motive unworthy or unbecoming a Senator." Pursuant to that rule, Warren was ordered to sit down and forbidden from speaking during the remainder 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."

McConnell later 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."

Overnight into early Wednesday, other Democratic senators continued speaking out against Sessions on the Senate floor and Sen. Jeff Merkley, D-Ore., read parts of King's 10-page letter - but not the excerpts Warren had read aloud.

Other Democrats, including Kamala Harris, Calif., and Sheldon Whitehouse, R.I., had come to Warren's defense by trying to have King's entire letter placed into the Senate record or to allow Warren to continue participating. But Republican senators objected.

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.

Warren tweeted: I will not be silent about a nominee for AG who has made derogatory & racist comments that have no place in our justice system.

Banned from reading King's letter on the Senate floor, Warren instead went to a nearby room and read it aloud on Facebook Live.

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 intensified 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.

Heidi Feldman, 51, arrived at home, checked social media, and saw news of what had happened to Warren. Instantly, she decided to head to the Capitol and read King's letter out loud, to whoever might want to listen.

"I've been an increasingly political active person since 2008," said Feldman, a Georgetown Law professor. "I marched in the Women's March, and I've organized law students. I just felt that I had to do this."

Feldman tweeted her plans and location, and arrived on the lawn south of the Senate at 10:15 p.m. Not long after, a dozen protesters joined her, taking turns reading from the letter.