There have been few moments like the one descending on Washington.

Nearly three weeks after the Senate Judiciary Committee wrapped up its confirmation hearings on Supreme Court nominee Brett Kavanaugh, he is being brought back before the panel Thursday — along with Christine Blasey Ford, who has accused him of sexually assaulting her when they were in high school — to try to clear his name. The nominee's appearance comes amid new allegations Wednesday.

"The hearing we are about to witness is unprecedented in modern Senate history," said Ron Bonjean, a former aide to Sen. Trent Lott who led the communications effort for Justice Neil Gorsuch's confirmation hearings.

"It remains a jump ball on how this hearing will turn out," he added, "but the pressure will be on Dr. Ford to provide corroborated and substantiated evidence backing up her allegation against Kavanaugh."

At the Capitol, a Supreme Court seat — and a conservative majority on that court — hangs in the balance.

At the other end of Pennsylvania Avenue, President Donald Trump may be weighing the fate of Deputy Attorney General Rod Rosenstein, who oversees special counsel Robert Mueller's investigation of Russian election meddling and Trump.

Together, Kavanaugh and Rosenstein represent a highly unusual convergence of constitutionally consequential events that could have significant implications for the future of Trump's presidency and beyond it.

Rosenstein's possible visit to the White House on Thursday — it has been scheduled but Trump said Wednesday he may delay it because of the Kavanaugh hearing — would be his first face-to-face meeting with Trump since reports surfaced last week that the deputy attorney general had discussed wearing a wire to secretly record the president and raised the possibility of invoking the 25th Amendment to push him from office.

Some allies of Trump see those revelations as justification for firing Rosenstein — who has drawn Trump's wrath for protecting Mueller and for not taking action against officials the president believes conspired against him — while others worry that it would be legally fraught to try to derail a probe looking into whether Trump obstructed justice.

The president said Wednesday he hopes that Rosenstein stays on, but Trump declined to answer directly when asked about this future. "We'll see," Trump said.

Trump and GOP leaders are anxious to hold a confirmation vote on Kavanaugh. They are worried about the possibility that a justice delayed could be a justice denied if Democrats win control of the Senate in the midterm elections.

"If there's a delay, there's going to be such a revolt in Republican circles you won't believe it," Matt Schlapp, chairman of the American Conservative Union, said in a telephone interview with NBC News. "Sometimes you gotta force the vote."

Already, Senate Majority Leader Mitch McConnell, R-Ky., has promised a swift confirmation of Kavanaugh after the hearing Thursday — regardless of the testimony — and Trump said Wednesday that the Senate should have voted already.

"They could’ve pushed it through two-and-a-half weeks ago, and you wouldn't be talking about it right now, which is, frankly, what I would've preferred," Trump said.

Judiciary Committee Republicans have created rules for the unusual hearing — just the two main witnesses and the deputization of a female sex-crimes prosecutor to ask questions for the all-male GOP contingent — that all but guarantee a "he said, she said" dynamic pitting the professor's memories against the federal judge's denials.

"Up or down, yes or no, however this vote goes, I am confident in saying that it will forever be steeped in doubt," Sen. Jeff Flake, R-Ariz., a member of the Judiciary Committee, said on the Senate floor Wednesday.

"Something really awful would have to happen in those hearings for it to change people's minds, and I wouldn't wish that on either of the witnesses," said Linda Fowler, a government professor at Dartmouth College in Hanover, N.H.

While there's no perfect historical parallel for the Kavanaugh hearing, Senate committees have seen many do-or-die political moments, from Joe McCarthy getting hammered with the question of whether he had any "sense of decency" to Nixon White House aide Alexander Butterfield revealing "everything was taped" during Watergate.

The comparison most often drawn is between this hearing and that of Anita Hill, who accused current Supreme Court Justice Clarence Thomas of sexual harassment when he was nominated for the court nearly three decades ago.

But there was another confirmation hearing, a few years before that, that also turned on personal behavior and the credibility of the nominee. And it went like this:

President George H.W. Bush's pick to run the Pentagon, John Tower, a former GOP senator from Texas, was on the ropes, his nomination bedeviled by allegations of alcohol abuse, sexual misconduct and indebtedness to defense contractors.

At a February 1989 hearing, Georgia Democrat Sam Nunn, chairman of the Senate Armed Services Committee, asked Tower point-blank whether he had a drinking problem.

"I have none, sir," Tower replied. "I am a man of some discipline."

His response was unconvincing — and his nomination was voted down, 53-47, on the Senate floor.