Now, the billionaire private-equity titan has accused his former partner and Apollo Global Management Inc. co-founder Josh Harris of being behind a “malicious” campaign to take him down.

The allegation is laid out in a new court filing by Black’s legal team, as he fights civil claims from a former Russian model, Guzel Ganieva, who’s accused him of sexual assault. Black has said their yearslong affair was consensual and she tried to extort him. And in a countersuit last year, he said unidentified public relations specialists and an unnamed funder were supporting her litigation in a scheme to destroy his reputation.

In a filing late Tuesday, Black’s attorneys accused Harris of embarking on a “coup and smear campaign” in a failed attempt to become Apollo’s chief executive officer. 

They allege Harris worked with public relations specialist Steven Rubenstein to seed stories in the media about Black’s past business ties with sex offender Jeffrey Epstein. But after Apollo commissioned a review that cleared Black of impropriety, Black arranged for another founder, Marc Rowan, to become CEO last year—leaving Harris on the outs.

Now, Black’s attorneys are demanding phone records as they look to prove that Ganieva also is working with Rubenstein—and by extension, has ties to Harris.

A representative for Harris, reached Wednesday, called the accusations “desperate and absurd.” And an attorney for Rubenstein said the PR specialist has “absolutely no relationship” to Ganieva.

In their filing seeking documents, Black’s lawyers insisted that phone records could “show communication between Ms. Ganieva’s camp and Mr. Rubenstein’s camp—between his accuser and the public relations team that works for his archrival—further demonstrating that Ms. Ganieva’s claims are nothing but fabrications stitched together from whole cloth.”

“It is not a stretch,” Black’s lawyers added, “to infer that someone with very deep pockets is supporting her and/or this lawsuit. Mr. Black is entitled to probe and prove up that inference.”

The drama between Black, 70, and Ganieva has been escalating for months in explosive back-and-forth lawsuits—starting with revelations about Black’s extramarital relationship and now evolving into a rare case of a Wall Street titan accusing a former colleague of orchestrating a campaign to bring him down.

Ganieva’s lawyers have disputed Black’s claims that her case is being supported by a funder as “pure speculation,” recently asking a judge to throw out his lawsuit. She sued him last year for defamation, intentional infliction of emotional distress, gender-motivated violence and retaliation. 

“The claims in Mr. Black’s legal memorandum are baseless, untrue and totally unsupported,” Jonathan Rosen, a spokesman for Harris, said in a statement. 

“Mr. Harris does not know Ms. Ganieva, has never met or spoken with her or anyone representing her, has no financial or any other dealings with her or her representatives, and had no involvement of any kind in the filing of any claims by her. Simply put, Mr. Harris has nothing whatsoever to do with the deeply troubling situation Mr. Black finds himself in, and any statement or implication otherwise is unhinged at best.”

Evan Farber, a lawyer for Rubenstein, also disputed Black’s allegations. 

“Mr. Rubenstein and his firm have had absolutely no relationship with Ms. Ganieva, past, present, formal or informal,” Farber said in a statement. “These, and the rest of the claims filed by Mr. Black’s attorneys, offer a concocted, ever-evolving conspiracy theory, packed with false information, and are not based in reality.”