“Obviously Mitch has got his heart and soul in this,” said Senator Johnny Isakson, Republican of Georgia. “He’s done everything he could. He’s done a tremendous job of fairly handling the unforeseen but challenging things that have happened. I think he’s acquitted himself well as a leader regardless of whether or not he’s successful on the vote.”

Democrats find Mr. McConnell’s complaints that Judge Kavanaugh is being treated unfairly and that they are conspiring to destroy and delay an outstanding nominee a little hard to take given that Mr. McConnell was the mastermind of the decision to block President Barack Obama’s 2016 nomination of Merrick B. Garland and hold the seat open for a Republican president to fill.

“From the man who single-handedly delayed the filling of Justice Scalia’s seat for 10 months to complain about a one-week delay to get the truth — give me a break,” Senator Chuck Schumer of New York, the Democratic leader, said Wednesday. “It is classic diversionary, blame-the-other-person tactics when he himself is the master of delay. It is galling, appalling, to hear day after day the majority leader get on his high horse about delay, when he almost invented the word when it comes to judicial nominations.”

The nomination has not gone the way that Mr. McConnell envisioned despite his initial warnings to the White House that Judge Kavanaugh’s long history and paper trail in Washington would present complications. Still, despite objections by Democrats that he had lied to the Judiciary Committee about his service in the administration of President George W. Bush, Judge Kavanaugh seemed a shoo-in. Then a letter surfaced from Christine Blasey Ford accusing him of sexually assaulting her when they were both teenagers, she stepped forward, and the confirmation struggle took an extraordinary turn.

Even after the accusations became public, Mr. McConnell said that Republicans were going to “plow right through it” while guaranteeing that “in the very near future,” Judge Kavanaugh would be taking his seat on the court. With such uncertainty enveloping the nomination, Mr. McConnell has recalibrated his message and is now only guaranteeing that there will be a vote as soon as this week.

Seemingly on the verge of victory last week, he also found his authority undercut by Mr. Flake and other Republicans who demanded a one-week delay for added investigation into the accusations instead of backing a final vote. Their position — and refusal to commit to Judge Kavanaugh without more investigation — meant Mr. McConnell had to readjust his plans while warning that Democrats would not be satisfied with any inquiry and would use the added time to raise new objections.