(CNN) The Senate Judiciary Committee will vote on whether to favorably recommend Brett Kavanaugh's nomination to the Supreme Court as previously scheduled Friday morning, though top GOP senators did not know as of Thursday night whether enough key Republican votes had been convinced to confirm President Donald Trump's nominee.

Kavanaugh's supporters and critics are now closely watching a handful of key Republican senators as they decide whether to support the nominee, following a day-long, blockbuster hearing that featured both Kavanaugh and the woman who accused him of sexual assault.

The vote scheduled for Friday morning means undecided GOP members of the committee -- including Arizona Republican Sen. Jeff Flake -- have just hours to publicly choose a side in a deeply polarizing political fight.

As of Thursday night, Flake -- who also met earlier with fellow key votes Republican Sens. Susan Collins and Lisa Murkowski and Democratic Sen. Joe Manchin -- told reporters, "There's more doubt than certainty moving ahead."

"This isn't easy for anybody," Flake told reporters. "Some of us have been talking for a while -- similar questions I guess."

When asked if he thought more time before the deadline would help with his decision, Flake said he didn't know.

"When you have more time, you look at what more time has done in the past couple of days in term of ludicrous allegations, some of which have been recanted. Others just were anonymous to begin with, and what does that do to the accused. Just to give it more time. I don't know. You have to weigh those things, You have to weigh all those things."

GOP senators told reporters that members meeting behind closed doors said the committee vote would happen as previously scheduled Friday morning and that the first procedural vote will take place on the Senate floor Saturday. GOP leaders had pushed for a full Senate vote on Tuesday, October 2.

Senate Majority Leader Mitch McConnnell would not confirm if he had the votes following a conference wide meeting Thursday night.

When asked if he was confident the nomination would advance out of committee, he replied: "well the next step is the committee will be voting in the morning."

He added, "We're optimistic, basically."

'We're meeting at 9:30'

Senate Judiciary Committee chairman Chuck Grassley declined to answer questions Thursday night from reporters as he repeatedly said, "we're meeting at 9:30" -- a reference to the committee meeting where the panel is scheduled to vote on whether to give Kavanaugh a favorable recommendation.

When asked by the media if the nomination will come to the full Senate floor for a vote, Grassley responded "Depends on what happens tomorrow."

Republicans can advance Kavanaugh's without any support from Democrats, but given their 51-49 seat majority in the chamber, Kavanaugh's supporters can only lose one vote and still advance his nomination.

Sen. John Cornyn, who as majority whip is the second-ranking GOP member in the chamber, expressed optimism following a Republican meeting Thursday night that Kavanaugh's nomination will be favorably reported out of the committee on schedule.

Asked if he is confident that Kavanaugh can advance out of the committee, he said, "I am optimistic, yes."

At least one long-undecided Republican senator, Bob Corker of Tennessee, announced his support for Kavanaugh just before 9 p.m. ET on Thursday night.

"While both individuals provided compelling testimony, nothing that has been presented corroborates the allegation," Corker said in his announcement. "There is no question that Judge Kavanaugh is qualified to serve on the Supreme Court, and in a different political environment, he would be confirmed overwhelmingly."

Four key senators meet

The meeting of Flake, Collins, Manchin and Collins occurred less than hour after Kavanaugh finished his testimony before the Judiciary Committee , where he forcefully and passionately maintained his innocence and defiantly challenged Democratic senators who grilled him on multiple allegations of inappropriate behavior.

On Thursday morning, that same committee heard from Ford, who she said was "100%" certain Kavanaugh sexually assaulted her when they were teenagers in the 1980s. In Kavanaugh's testimony, he also said he was "100%" sure he did not sexual assault anyone.

Collins and Murkowski have appeared to be the most outspoken Republican senators in seeking additional investigation into the allegations of inappropriate behavior that have surfaced against Kavanaugh in recent days.

Multiple sources familiar with a private Wednesday meeting -- the night before the hearing -- told CNN that Collins appeared unnerved by the latest allegations, citing in particular that a sworn statement from accuser Julie Swetnick sent to the panel, which carries with it the possibility of perjury for lying to Congress. At that Wednesday meeting of Republican chairmen, GOP leaders tried to reassure Collins, keenly aware of the critical role she plays.

When asked by reporters earlier this week whether there should be a full FBI investigation into the allegations, Murkowski responded, "It would sure clear up all the questions, wouldn't it?"

On Thursday night, Murkowski said she was leaving to think over the nomination at home.

"I'm going to go home, have dinner and have a chance to think about all that's gone on today," Murkowski told reporters.

Manchin is up for re-election this fall in a state Donald Trump won overwhelmingly and supported Trump's last Supreme Court nominee Neil Gorsuch. Manchin was among a handful of Democrats from red and purple states that Kavanaugh supporters were targeting as possible votes.

"We are still talking," Manchin told CNN leaving that meeting. "There are no decisions on anything. There are some concerns that people have and we're going to try to close the loop."