Washington (CNN) Republican Sen. Jeff Flake of Arizona said Friday that an FBI investigation into allegations against Brett Kavanaugh could change his mind on the Supreme Court nomination, which he had said earlier in the day he would support.

Asked by CNN if he could change his vote and oppose the nomination depending on what he learns, Flake responded, "Sure, you bet -- that's why we are doing an extended background investigation."

Earlier Friday, Flake, who sits on the Senate Judiciary Committee, announced that he would vote to confirm Kavanaugh. But after being confronted by angry protestors, Flake called for a delay of the floor vote so that the FBI can investigate allegations Kavanaugh faces.

On Thursday, Christine Blasey Ford testified in front of the committee that the nominee sexually assaulted her at a social gathering in the 1980's. Kavanaugh vehemently denied the allegation.

Other women have also come forward with allegations against the nominee, including Deborah Ramirez who told The New Yorker that she remembers Kavanaugh exposing himself to her at a dormitory party. Kavanaugh has also denied that allegation.

Not long after Flake's call for an investigation, the Senate Judiciary Committee released a statement saying that the panel would request an investigation into "credible" allegations against Kavanaugh.

Flake told reporters that the protestors who confronted him earlier in the day did not change his mind necessarily and that he couldn't "pinpoint" the reason. But he said he has had sleepless nights. The Republican senator added that the FBI will determine what "credible" allegations to probe.

Republicans can confirm Kavanaugh without any Democratic votes, but with only a 51-49-seat hold on the Senate, Kavanaugh's supporters can only afford to lose one GOP vote and still advance his nomination.

Flake is not seeking re-election and will retire from the Senate at the end of his term in January.

"Yesterday, we heard compelling testimony from Dr. Ford, as well as a persuasive response from Judge Kavanaugh. I wish that I could express the confidence that some of my colleagues have conveyed about what either did or did not happen in the early 1980s, but I left the hearing yesterday with as much doubt as certainty," Flake said in his initial statement on Friday morning announcing his support for the nomination

"What I do know is that our system of justice affords a presumption of innocence to the accused, absent corroborating evidence. That is what binds us to the rule of law. While some may argue that a different standard should apply regarding the Senate's advice and consent responsibilities, I believe that the constitution's provisions of fairness and due process apply here as well," the statement said.

The Arizona Republican appeared torn after hearing Ford's testimony alleging that Kavanaugh sexually assaulted her in the 1980s -- and Kavanaugh's forceful denial. "This isn't easy for anybody," he told reporters on Thursday evening. "There's more doubt than certainty moving ahead."