WASHINGTON – One of Sen. Susan Collins' prominent challengers is slamming the Maine Republican for her vote in 2018 to confirm Supreme Court Justice Brett Kavanaugh following a new sexual misconduct allegation against him that surfaced over the weekend.

And in a statement provided to USA TODAY Monday evening, a spokesperson for Collins hit back against the recent reporting by the New York Times that has led to the blowback against Collins, saying "The news stories today are not adding anything to what has already been reported" and adding that "The only new part of the story was an alleged incident ... but this is an accusation that lacks an accuser."

Sara Gideon, speaker of the Maine House of Representatives, took to Twitter Sunday to criticize Collins' decision last year and to fundraise following the new revelation. Collins, a Republican, is up for re-election in 2020.

"I’m tired of hoping that Susan Collins does the right thing when she has shown time and time again that she puts Donald Trump and Mitch McConnell ahead of Mainers," Gideon wrote in a tweet.

The New York Times published an essay Saturday evening with new information about a prior claim of sexual misconduct against Kavanaugh that also included evidence supporting a previously unreported claim.

Kavanaugh has repeatedly denied sexual misconduct and sexual assault allegations against him. President Donald Trump and a number of Republicans have come to Kavanaugh's defense since the recent publication of the essay by the Times.

The essay is an adaptation from a forthcoming book about Kavanaugh written by two Times reporters. Collins spokesperson Annie Clark raised doubts about the book in a statement provided to USA TODAY Monday.

"The news stories today are not adding anything to what has already been reported. In fact, the NYT's own review of the book says that, 'In the end they [the authors] turn up no smoking gun, no secret confession, no friend who comes forth to say Kavanaugh was lying all this time,'" Clark said.

Clark continued: "The only new part of the story was an alleged incident reported by former Clinton aide Max Stier -- but this is an accusation that lacks an accuser. In fact, the New York Times corrected its own story to note that not only did the student in question not recall any such incident, she also declined to be interviewed for the book."

And the president has aggressively come to Kavanaugh's defense, also suggesting doubts about the Times' reporting. "Brett Kavanaugh should start suing people for libel, or the Justice Department should come to his rescue," Trump wrote in a tweet Sunday. "The lies being told about him are unbelievable."

And Trump tweeted again Monday. "The one who is actually being assaulted is Justice Kavanaugh," Trump posted. "Assaulted by lies and Fake News! This is all about the LameStream Media working with their partner, the Dems."

More:Trump says Kavanaugh is the one 'actually being assaulted' after new allegation of sexual assault

Since the essay's publication, some Democrats have called for Kavanaugh to be impeached.

More:Democrats are calling for Brett Kavanaugh to be impeached. How would that work?

Gideon, a Democrat, has repeatedly criticized Collins for voting to confirm Kavanaugh. Gideon is a part of a handful of challengers who announced they were going to run against Collins due to her decision to vote for Kavanaugh.

Ahead of Kavanaugh's confirmation vote last year, Collins gave a nearly 45-minute speech on the Senate floor detailing why she decided to support his nomination to the Supreme Court. Prior to that, it was unclear whether Collins would support Kavanaugh's confirmation.

More:Democratic presidential candidates want Kavanaugh impeached after newly surfaced sexual misconduct accusation

Several weeks ago, Collins said that she was that 'sad' that her vote for Kavanaugh may have cost her voters in next year's election.

“Have I lost some votes because of my decision to support Justice Kavanaugh? Yes, I have,” she said in an interview with Politico. “And I’m sad about that because I explained in great depth my decision-making.”

Contributing: Christal Hayes, David Jackson, Nicholas Wu and Jeanine Santucci, USA TODAY