The actress has alleged that after coming out with sexual assault charges against Weinstein, Jennifer Siebel Newsom called her and asked what she could offer to "make her happy."
It comes only two days before an increasingly tight recall election that will see a whopping 46 candidates try to unseat Newsom.
In an interview on the Rubin Report on YouTube, McGowan told Dave Rubin, "So this woman, I don’t know, some blonde lady name with the last name of the Newsom, cold-calls me, and was like, David Boies wants to know what it would take to make you happy."
Financial disclosures obtained by the Washington Free Beacon reveal that Boies has transferred Newsom gifts, including rare bottles of wine.
A report from The New Yorker also showed that in 2017, Boies tried to "dig up dirt" on Weinstein accusers to smear their credibility.
McGowan further posted a video to Twitter on Thursday crashing the current governor and his wife as a "fraud."
She announced: "Governor Gavin Newsom you're facing a recall because you're a fraud, just like your wife, Jennifer Siebel Newsom.
"I have the receipts. I wish I didn't. I wish you were all real. I wish you really did help.
"But you don't. And you're on the wrong side of wrong," she added.
Elder told Fox LA that he had not verified McGowan's charges, yet that she had produced emails from Jennifer Siebel Newsom.
Elder announced the charges, "Now I don't know whether it's true that Gavin Newsom's wife called on behalf of Harvey Weinstein's lawyer and tried to get Rose McGowan and tried to get her to back off of her allegations six months before the allegations blew up."
But he continued: "Rose McGowan has produced emails that were sent to her from Gavin Newsom's wife suggesting that they were having some sort of correspondence.
"What in the world is Gavin Newsom's wife doing contacting Rose McGowan, who made serious allegations of sexual harassment, if not rape, of Harvey Weinstein, who currently is facing several charges of rape as we speak?"
Elder and McGowan will speak to the media together at the Luxe Hotel Sunset Boulevard in Los Angeles on Sunday afternoon.
Meanwhile, McGowan declared at the event Sunday that she was no longer a Democrat. She also said that despite having some different policy views than Elder, she thought he was "the better candidate and the better man."
McGowan specifically took issue with the media and White critics disagreeing with his message as a Black man simply because he disagrees with the Black Lives Matter movement.
"Understand who it's coming from and that he might just know more than you living in a different skin," McGowan said.