Washington (CNN) Republican Sen. Lisa Murkowski of Alaska described President Donald Trump's Supreme Court nominee Brett Kavanaugh as "not the right man for the court at this time" and strongly signaled she will vote no in Kavanaugh's final confirmation vote on the US Senate floor.

After opposing a key procedural vote Friday morning on the nomination, Murkowski explained her vote to reporters, calling it "the most difficult evaluation" she has had to make.

"I believe that Brett Kavanaugh is a good man. I believe he is a good man. It just may be, that in my view, he's not the right man for the court at this time," the Alaska senator said.

Murkowski appears to be the sole Republican senator expected to vote against Kavanaugh's confirmation, eliciting criticism from some conservatives. Former Alaska governor and Republican vice presidential Sarah Palin nominee, a long-time political foe of the Murkowski family, suggested she might challenge the incumbent senator when she's up for re-election.

Murkowski's stance broke with the other three previously undecided senators who announced their decisions Friday. Republican Sens. Jeff Flake of Arizona and Susan Collins of Maine and West Virginia Democrat Joe Manchin all said they intended to back Kavanaugh, putting him on track for confirmation barring a last-minute development.

In a dramatic Friday morning vote, the Senate moved to end debate on the Kavanaugh nomination and advance to a final confirmation vote, which could take place as soon as Saturday.

Murkowski sat quietly as the roll was called for the Friday vote. When her name was called, she stood up slowly, paused, then said "no" and slowly sat back down. Others in the gallery could hardly hear her.

After the vote, Murkowski stayed and talked to varying members of GOP leadership for more than 20 minutes. At one point, she and Senate Majority Leader Mitch McConnell talked one-on-one. She patted him on the shoulder as they split up.

Murkowski had been one of a handful of pivotal senators who remained publicly undecided on the nomination in the days leading up to Friday's vote.

The other senators who have been closely watched since it was not known how they would vote -- Republican Sen. Susan Collins of Maine and Democratic Sen. Joe Manchin of West Virginia -- all voted "yes" on Friday. Republican Sen. Jeff Flake of Arizona also said on MSNBC on Friday he would vote yes on Kavanaugh's final confirmation barring no late breaking developments.

In explaining her vote to reporters, Murkowski said on Friday that she had not come to a decision on how she would vote until walking into the Senate floor that morning. She said that the process had not been "fair" to Kavanaugh, but that ultimately it had become about something "bigger than a nominee."

"This hasn't been fair to the judge, but I also recognize that we need to have institutions that are viewed as fair," she said. "If people who are victims, if people who feel there is no fairness in our system of government, particularly within our courts, we've gone down a path that is not good and right for this country."

She went on to say, "I have been wrestling with whether or not this was about the qualifications of a good man or is this bigger than the nominee. And I believe we are dealing with issues right now that are bigger than a nominee, and how we ensure that our institutions, not only the legislative branch but our judicial branch, continue to be respected."

While it wasn't entirely clear which issues Murkowski was addressing, her comments could be a reference to the #MeToo movement which has shaken institutions across the country and around the world for the past year. Kavanaugh's nomination has been slowed by an allegation of sexual assault and accusations of sexually inappropriate behavior, allegations he has vehemently denied.

A reporter with Alaska Public Media recently asked Murkowski if she had ever had her own #MeToo moment. The senator said "yes," but declined to elaborate.

In a sign of the political pressure the Alaska Republican faces, a variety of activists and constituents showed up at her Washington, DC, Senate office throughout Friday morning before and after the vote. Some wore shirts that said "Confirm Kavanaugh Now," and "I stand with Brett," while others had buttons that said, "Believe Survivors."