Republican senators don't know if they have the 50 votes needed to confirm Supreme Court nominee Brett Kavanaugh.

But many Republicans believe they'll know after Thursday, when both Kavanaugh and the woman accusing him of sexual assault, Christine Blasey Ford, testify at a high-stakes Judiciary Committee hearing.

That makes the hearing a critical moment in Kavanaugh's increasingly troubled nomination, and one that will hinge not on the sparse evidence both sides have provided from the alleged 1982 incident, but on how they perform, and who delivers a more credible performance.

“I’d like to see the demeanor of the witnesses,” Sen. Richard Shelby, R-Ala., said Wednesday.

Sen. Bob Corker, R-Tenn., said he’d be watching the hearing very closely. "I’ve cleared my schedule and I’m going to watch the hearing from start to finish."

Republican leaders last week were making noises about quickly considering Ford's allegations that Kavanaugh tried to rape her when they were teenagers, and then moving to a vote. But Kavanaugh's fate seemed less certain this week, especially after more sexual assault allegations piled up against him, and more questions were raised about how much time senators might need to sort through them.

Thursday's hearing could end up being the first step of many to get to the bottom of it all, but as of Wednesday, Republicans were saying they first wanted to hear from both Kavanaugh and Ford before making any decisions.

Sens. Susan Collins of Maine and Lisa Murkowski of Alaska have made it clear they want to be certain about Kavanaugh in light of Ford's claims.

“We’ll have to see if she brings forward the allegations,” said Murkowski, who has not said which way she's leaning.

Other GOP senators agreed, including Sens. Jeff Flake of Arizona and Marco Rubio of Florida.

“Like anybody else, I’m going to watch the hearing tomorrow,” Rubio said Wednesday. “And I’ll have a further comment about the nomination after the hearing completes.”

Flake sits on the Senate Judiciary Committee, where his "no" vote would likely prevent the committee from formally supporting Kavanaugh. The committee is made up of 11 Republicans and 10 Democrats.

Even Sen. Orrin Hatch, R-Utah, who has been highly critical of the accusations, said he’d listen to both witnesses "and then make up my own mind about it."

President Trump himself said Wednesday that he has an open mind about Kavanaugh and his accuser, and could be convinced to rethink his nomination depending on what the witnesses say.

“It’s possible they will be convincing,” Trump said of Kavanaugh’s accusers, although only Ford will testify on Thursday. “I have to see it.”

The uncertainty on the Republican side caps a hectic two weeks for Kavanaugh, who needs a simple majority vote in a 51-49 Senate in which he may not get any support from Democrats. Republicans can lose only one vote and still confirm Kavanaugh with the tie-breaking support of Vice President Mike Pence, but they'll need to pick up a Democratic vote for every Republican they lose after that.

Preparations for Thursday's hearing were taking place even as the committee was scrambling to get statements from two new accusers, and as Democrats called for the process to be delayed in light of the new accusations.

One of the new accusers was Deborah Ramirez, who claimed Kavanaugh exposed himself to her in college. The second was Julie Swetnick, who said Wednesday in an affidavit that Kavanaugh attended parties where women were molested and raped, and by the evening, a fourth anonymous accusation was brought to the Senate's attention.

Republicans were also fending off accusations that they were trying to create better optics for the hearing by having veteran sex crimes prosecutor Rachel Mitchell ask questions of Ford on behalf of the 11 Republican men on the committee. Panel Republicans interviewed by the Washington Examiner said they’ll defer completely to Mitchell, even as some Democrats complained that it's not fair to Ford to have a prosecutor do their job.

In spite of all the hurdles, Republicans are still in a position to hold a final confirmation vote by early next week, and some Republicans were steadfast in their support for Kavanaugh convinced that the nominee is a victim of politics.

Sen. Lindsey Graham, R-S.C., for example, questioned the third accuser’s story of attending multiple parties where alleged gang rapes occurred.

Senate Majority Whip John Cornyn, R-Texas, projected confidence by saying Republicans have reached out to Avenetti and are seeking to interview the new accuser at least at the staff level, “certainly by the time the Senate votes on Tuesday.”

But others said they made no judgment regarding Kavanaugh from the latest claim or about Michael Avenetti, who is representing the accuser and is a staunch opponent of President Trump.

“I don’t have any information about any of this except what has been reported,” said Sen. John Kennedy, R-La., a member of the Judiciary Committee. Kennedy said “I don’t know” when asked if the latest accusation is politically motivated.

Republicans huddled Wednesday in a closed-door lunch near the Senate chamber with Vice President Mike Pence to talk about the hearing, how it would proceed, and what the committee was doing in response to the latest allegations.

“We are proceeding normally, just as we would on any other allegation,” Kennedy said after the lunch.

When the hearing convenes, each lawmaker will be provided five minutes of questioning for Kavanaugh and another five minutes to question Ford.

The hearing will take place in a small meeting room in a Senate office building. The massive swarm of press coverage will be greatly curtailed by strict limitations, at the request of Ford’s team of lawyers.

Al Weaver contributed to this report.