Senator Elizabeth Warren, Democrat of Massachusetts, had been holding forth on the Senate floor on the eve of Mr. Sessions’s expected confirmation vote, reciting a 1986 letter from Mrs. King that criticized Mr. Sessions’s record on civil rights.
Sensing a stirring beside her a short while later, Ms. Warren stopped herself and scanned the chamber.
Across the room, Senator Mitch McConnell, the majority leader, had stepped forward with an objection, setting off an extraordinary confrontation in the Capitol and silencing a colleague, procedurally, in the throes of a contentious debate over President Trump’s cabinet nominee.
“The senator has impugned the motives and conduct of our colleague from Alabama, as warned by the chair,” Mr. McConnell began, alluding to Mrs. King’s letter, which accused Mr. Sessions of using “the awesome powers of his office in a shabby attempt to intimidate and frighten elderly black voters.”
Mr. McConnell called the Senate to order under what is known as Rule XIX, which prohibits debating senators from ascribing “to another senator or to other senators any conduct or motive unworthy or unbecoming a senator.”
When Mr. McConnell concluded, Ms. Warren said she was “surprised that the words of Coretta Scott King are not suitable for debate in the United States Senate.” She asked to continue her remarks.
Mr. McConnell objected….
“She was warned,” Mr. McConnell said of Ms. Warren. “She was given an explanation. Nevertheless, she persisted.”
Democrats planned to hold the floor into the wee hours of Wednesday to protest Mr. Sessions’s nomination.