Kavanaugh has sternly denied the accusation.
"I categorically and unequivocally deny this allegation," Kavanaugh said in a statement issued late last week to news organizations, when the story first arose. "I did not do this back in high school or at any time.”
Democrats said the turn of events should delay action on Kavanaugh's nomination.
"At a bare minimum, this week’s scheduled committee vote on Judge Kavanaugh’s lifetime appointment to the Supreme Court must be postponed until this matter is fully and thoroughly investigated," said Sen. Cory Booker (D-NJ).
"We cannot meet our constitutional responsibility of advice and consent without a fair and careful review of the serious and credible allegations made by Dr. Ford," said Sen. Dick Durbin (R-IL).
On their own, Democrats are powerless to stop the nomination - making the statement by Sen. Flake all the more important as to Kavanaugh's future.
But the he-said-she-said nature of the allegations - and their sudden appearance - left other Republicans wondering if this was a Political Hail Mary.
As of now, it hasn't changed the approach of key GOP Senators like Sen. Susan Collins (R-ME) - but could change the thinking of Sen. Lisa Murkowski (R-AK).
"It’s disturbing that these uncorroborated allegations from more than 35 years ago, during high school, would surface on the eve of a committee vote after Democrats sat on them since July," said a spokesman for Sen. Charles Grassley (R-IA), the chairman of the Senate Judiciary Committee.
"It raises a lot of questions about Democrats' tactics and motives," the spokesman, Taylor Foy, added.
Grassley's office told the Associated Press that it was possible committee members might have a bipartisan call with Ford, though nothing final had been announced as of Sunday evening.
The last minute nature of these charges has some similarities to the firestorm that erupted over the nomination of Justice Clarence Thomas in 1991.
As with Kavanaugh, Thomas's testimony was completed before Hill made public accusations of sexual harassment against Thomas.
The Senate Judiciary Committee reconvened to hear those allegations, as Hill and Thomas told their stories. Thomas was ultimately approved on a narrow 52-48 vote in the full Senate.