Swetnick is being represented by high-profile attorney Michael Avenatti, who called his client "courageous, fearless and honest".
Mr Kavanaugh has been accused of sexual misconduct by two other women, putting his nomination for the high court at risk.
Mr Avenatti declined to expand on the allegation in an interview on ABC's The View, saying he would not add detail beyond what was in the statement.
The affidavits signed Monday and Tuesday of this week could give more weight to Ms Ford's story on the eve of her testimony - and Mr Kavanaugh's expected denial - before the Senate Judiciary Committee on Thursday.
Trump called the allegations against Kavanaugh "false accusations", but stopped short of calling his accusers liars.
And on Wednesday, a woman represented by Mr Avenatti - who shot to fame as the lawyer taking on the president for porn actress Stormy Daniels - made another accusation of misconduct.More news: Fortnite V5.40 Adds Suave Suits and Grappling Guns
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"[Senate Judiciary] Committee staff have a second interview with a man who believes he, not Judge Kavanaugh, had the encounter with Dr. Ford in the summer of 1982 that is the basis of her allegation", Everett wrote.
In his declaration, Koegler said he met the Fords while coaching their son's baseball team more than five years ago.
She also says she told at least two people about this shortly afterward but does not name them. She witnessed both of them "drink excessively and "engage in highly inappropriate conduct". Susan Collins (R-Maine) told reporters she was "appalled" by his remarks.
President Donald Trump, who is in NY attending the annual UN General Assembly session, came out in support of his Supreme Court nominee and slammed Avenatti. That made it sound like they're just going through the motions with today's hearing and will vote to confirm the judge regardless of what Ford says.
Judge Kavanaugh has also been accused of exposing himself to a classmate, Deborah Ramirez, during an alcohol-fueled Yale University party a few years later.
He also asked that her privacy and the privacy of her family be respected.
The Republican governor said senators should pursue a thorough investigation into the allegations of sexual misconduct involving Kavanaugh.
Republicans hold a 51-49 advantage in the Senate and can't afford more than one defection to ensure confirmation without Democratic support.