Wall Street's billionaire soap opera gets messier

The backroom fight between Apollo Global Management co-founders Leon Black and Josh Harris has tumbled out into the open, providing plenty of free material to the writers of Wall Street soap operas like "Billions" and "Succession."

Why it matters: This is shaping up to become the messiest fight in private equity's 45-year history.

What to know: Apollo isn't a party to any of the related lawsuits, and is trying to portray this as an arms-length dispute between what it calls "two former employees." But Harris remains on the publicly-traded firm's board of directors, and current CEO Marc Rowan (the firm's third co-founder) was coaxed out of Hamptons retirement by Black.

• In other words, the calls are still coming from inside the house.

Background: A model named Guzel Ganieva last July sued Black, who at the time was still Apollo's CEO, for defamation and sexual assault. Black, who had previously admitted to having an affair with Ganieva, countersued by denying the assault allegations (which are explicitly horrific) and calling her complaint an extortive "work of fiction."

• Black's response also noted that he was seeking to learn if Ganieva "is acting alone or is working in concert with" others.
• This felt like code for "I'm looking into Josh," as there were plenty of murmurs that Harris had been a driving force behind an Apollo investigation into Black's dealings with Jeffrey Epstein. Moreover, Harris was widely believed to be angling for the CEO job that ultimately went to Rowan.

Fast forward: In a court filing last week, Black accused Harris of orchestrating a "coup" and "malicious campaign," insinuating that Harris had a role in Ganieva's legal actions. A Harris spokesperson tells the WSJ that he has "no involvement of any kind in the filing of any claims by her."

• Black's filing also says that Apollo was founded only by Black and Rowan, with Harris joining "soon afterwards as a junior employee." It's worth noting that Apollo, while run by Black, regularly referred to Harris as a "co-founder" in securities filings (including its IPO registration statement).

The bottom line: Apollo is the oldest private equity firm to have not successfully set up a founder succession plan, and that failure is set to play out in a courtroom.