A slew of prominent Democrats called on Congress to impeach Supreme Court Justice Brett Kavanaugh after allegations of sexual misconduct that had once threatened to torpedo his nomination to the bench resurfaced, even as President Donald Trump continued to defend him.

"I sat through those hearings," Sen. Kamala Harris, a member of the Senate Judiciary Commitee and a Democratic presidential candidate, tweeted on Sunday. "Brett Kavanaugh lied to the U.S. Senate and most importantly to the American people. He was put on the Court through a sham process and his place on the Court is an insult to the pursuit of truth and justice. He must be impeached."

Kavanaugh was nominated by Trump after the retirement of Justice Anthony Kennedy, a swing vote on the court. He was sworn in last October after a confirmation process that focused on the allegations — and the protests, controversy and high drama of the Senate hearing that followed.

The new revelations came to light in an opinion-section article written by two New York Times reporters, published late Saturday, whose book on the Kavanaugh nomination will be released this week. In the book, which was summarized in Saturday's article, the authors wrote that they had found new corroboration for accusations that Kavanaugh exposed himself to Deborah Ramirez, a classmate at Yale. NBC News has not verified that reporting.

The book, written by Robin Pogrebin and Kate Kelly, also uncovered a new accusation. Citing two officials, the reporters said that former Yale classmate Max Stier told senators and the FBI about a different episode of alleged sexual misconduct. Two people with first-hand knowledge confirm to NBC News that the FBI was notified of Stier's claim.

The FBI was made aware of the allegation during the first few days of the supplemental investigation the bureau was asked to conduct by the Senate Judiciary Committee in the midst of his contentious confirmation hearing, according to the two people familiar with the allegations.

Stier declined a request for comment from NBC News. The FBI did not immediately respond to a request for comment.

Kavanaugh has strongly denied the allegation by Ramirez as well as accusations by Christine Blasey Ford that he sexually assaulted her when the two were in high school. Ford testified publicly during Kavanaugh's confirmation process in a widely watched, emotional Senate hearing.

Reached through the Supreme Court, Kavanaugh declined to comment to NBC News on Sunday.

Brett Kavanaugh delivered a broad denial of misconduct during his confirmation hearing last year.

The new allegations tore through Washington on Sunday, with many Democrats calling for Congress to take action.

Sen. Elizabeth Warren, D-Mass., tweeted that, "Confirmation is not exoneration, and these newest revelations are disturbing. Like the man who appointed him, Kavanaugh should be impeached."

Vermont Sen. Bernie Sanders, also a presidential hopeful, tweeted that, "The revelations today confirm what we already knew: During his hearing, Kavanaugh faced credible accusations and likely lied to Congress. I support any appropriate constitutional mechanism to hold him accountable."

Trump lashed out at the new reporting, calling Kavanaugh "an innocent man."

"He is an innocent man who has been treated HORRIBLY," Trump said on Twitter, referring to the accusations as "lies." The president also accused critics of attempting to influence Kavanaugh's opinions and suggested that Kavanaugh "start suing people for libel, or the Justice Department should come to his rescue."

Now the Radical Left Democrats and their Partner, the LameStream Media, are after Brett Kavanaugh again, talking loudly of their favorite word, impeachment. He is an innocent man who has been treated HORRIBLY. Such lies about him. They want to scare him into turning Liberal! — Donald J. Trump (@realDonaldTrump) September 15, 2019

Brett Kavanaugh should start suing people for libel, or the Justice Department should come to his rescue. The lies being told about him are unbelievable. False Accusations without recrimination. When does it stop? They are trying to influence his opinions. Can’t let that happen! — Donald J. Trump (@realDonaldTrump) September 15, 2019

Kavanaugh told the Senate Judiciary Committee under oath last year that the first time he heard of Ramirez’s allegation was in a Sept. 23 article in The New Yorker.

But according to text messages obtained last year by NBC News, in the days leading up to Ramirez' public allegation Kavanaugh and his team were communicating behind the scenes with friends to refute the claim.

The FBI opened an expanded background investigation into Kavanaugh after pressure from Democrats in Congress initially delayed his confirmation process.

But dozens of people with potential information into the allegations against him were not contacted, according to multiple sources that include friends of both the nominee and his accusers.

Sen. Mazie Hirono, D-Hawaii, who grilled Kavanaugh during his confirmation hearing, said on Sunday that the new reporting is more proof that "Brett Kavanaugh should never have been confirmed to the Supreme Court. It was plain to me and many others at the time that the FBI ‘investigation’ into the serious, corroborated allegations of sexual assault by Justice Kavanaugh was a sham."

"The House Judiciary Committee should immediately begin an impeachment inquiry to determine whether Justice Kavanaugh lied to Congress and why the FBI wasn’t permitted to investigate all credible allegations against him," she added.

Senate Majority Leader Mitch McConnell, R-Ky., defended Kavanaugh on Sunday, tweeting, "The far left’s willingness to seize on completely uncorroborated and unsubstantiated allegations during last year’s confirmation process was a dark and embarrassing chapter for the Senate."

"Fortunately a majority of Senators and the American people rallied behind timeless principles such as due process and the presumption of innocence," he wrote. "I look forward to many years of service to come from Justice Kavanaugh."