The latest claims of impropriety during Kavanaugh's youth came as he was already facing a dramatic hearing where his testimony was to be weighed against that of a university professor who has separately accused him of assault.
Senate Democrats are now investigating a bombshell claim by Deborah Ramirez, 53, who says Kavanaugh exposed himself to her during a 1980s college party at Yale University, thrust his genitals in her face and caused her to touch them without her consent, according to The New Yorker.
The story was denied by Kavanaugh, who called it "a smear, plain and simple."
"The people who knew me then know that this did not happen, and have said so," the conservative judge said in a statement.
Like Christine Blasey Ford, the professor accusing him of assaulting her when they were teenagers, Ramirez is calling for an FBI investigation into the incident, and Democratic lawmakers are backing their demand.
Ford agreed to testify Thursday after an increasingly ugly weeklong standoff that saw her forced to leave her California home as she faced death threats and the president openly attacked her credibility.
Kavanaugh, who strongly denies the assault allegation, has said he wishes to testify as soon as possible to clear his name from Ford's claims that he attacked her at a high school party in the 1980s.
The federal judge has calendars from the summer of 1982 he plans to share with senators showing he was out of town most of that time with no indication of the party of concern, The New York Times reported.
The two parties will testify separately -- first Ford, followed by Kavanaugh, who will respond -- the Senate Judiciary Committee confirmed.
Senator Dianne Feinstein, the top Democrat on the judiciary committee, urged the panel to halt proceedings in light of the latest allegation.
"I am writing to request an immediate postponement of any further proceedings related to the nomination of Brett Kavanaugh," she said in a statement.
"I also ask that the newest allegations of sexual misconduct be referred to the FBI for investigation, and that you join our request for the White House to direct the FBI to investigate the allegations of Christine Blasey
Confirmation in the balance
At stake is not only the fate of Trump's hand-picked Supreme Court nominee, but also Republican chances in November's midterm elections that face increased risk if the polarizing confirmation battle drags on.
Lindsey Graham -- a member of the panel that must approve Kavanaugh's nomination before it goes to the full chamber -- summed up the position of many Republicans by saying he did not expect Ford's testimony to change his mind.
"What am I supposed to do? Go ahead and ruin this guy's life based on an accusation?" he told "Fox News Sunday." "Unless there's something more, no, I'm not going to ruin Judge Kavanaugh's life over this."
According to a YouGov poll conducted for CBS, more than half of Americans want an FBI investigation before a vote on Kavanaugh, but more than two thirds of Republicans want a vote within days.
Republicans, who hold a paper-thin majority in the Senate, can ill afford defections if Kavanaugh is to be approved.
Danger of defections
"If one Republican senator should decide that Dr Ford's allegations, assertions, are true, and that they are serious, it could make a big difference in the nomination of Brett Kavanaugh," Democratic Senator Dick Durbin said on ABC's "This Week."
After days of relative restraint, Trump lashed at Ford on Friday, questioning the credibility of her allegations, and in doing so may already have hurt his nominee's chances with a senator from his own party.
Trump contended that Ford's decision to wait so late before going public shows the incident probably was not "as bad as she says" -- even if this runs counter to what experts say is the typical reaction of sexual assault victims afraid or embarrassed to report.
Susan Collins -- a Republican who sits on the Judiciary Committee -- said she was "appalled" by Trump's tweet, stressing that incidents of sexual assault were known to be chronically under-reported.
Trump's outburst saw an outpouring of sympathy for Ford -- and outrage at the president -- as thousands of women, and men too, shared why they had kept silent after being assaulted, under the Twitter hashtag #WhyIDidntReport.