The love rat TV host, 61, and third wife Marjorie, 53, moved from Atlanta to Los Angeles last year to launch the former stand-up comic's self-titled talk show.
But according to insiders, Steve's cozying up to the Kardashian momager during closed-door business meetings, endless phone chats and nonstop text messages has sent Marjorie over the edge.
"There was a huge blowout fight and Marjorie walked out threatening divorce," a source told Radar.
"There's no way she was going to put up with Steve hanging around a man-eater like Kris — especially since he's proven time and again he can't be trusted."
Steve and 62-year-old Kris, a two-time divorcée, have been buddy-buddy for years .
They were pictured together during Paris Fashion Week in 2015. They've also been seen out in Hollywood on multiple occasions and Kris appeared on his talk show to help boost ratings.
To further cement their relationship, Kris brought her brood to Family Feud.
Despite their apparent closeness, a TV insider insisted Kris has "no interest in Steve romantically."
Instead, crafty Kris is stringing Steve along, hoping to manipulate him into sharing his TV smarts so she can use his advice to boost her own sagging empire.
"Kris is pursuing Steve — but it's all about business," the source snitched. "She admires his TV success and wants to learn all his secrets."
Although Keeping Up with the Kardashians has been a monster hit, the show was created by Ryan Seacrest, and Kris desperately needs guidance to grow her own showbiz brand, according to sources.
"Kris has tried to produce a long list of shows, but they've all been disasters," the source said.
"Meanwhile, Steve has the golden touch when it comes to TV. That's why Kris is looking to him for professional help."
Furious over the pair's closeness, Marjorie got revenge by posting several videos of her working out with her hunky young personal trainer on Instagram.
A few days later, Steve made a spur-of-the-moment decision to treat Marjorie to a no-expense-spared vacation in Europe.
"Steve has a wandering eye and he loves women!" said a former employee on his talk show, who spoke with Radar on the condition of anonymity.
"He's cheated during his previous marriages, and Marjorie knows he could do it again. She knows her man's weakness — knows everything about him! That's why she watches him so closely."
Steve left his first wife, Marcia, in 1990 while she was pregnant to move in with Mary Shackelford, who became his second wife in 1996.
Before even filing for divorce, Steve ditched Mary in 2005 for Marjorie — and his bitter ex has never forgiven him.
Last year Mary socked Steve with a $60 million lawsuit, claiming he bullied her out of a fortune during their divorce and his cheating triggered a breakdown that landed her in a mental hospital.
Mary's sister, Ruth Littrell, fumed: "Once a cheater, always a cheater. Steve's up to his old tricks — it's nothing new. Marjorie will end up divorcing him and taking him for everything he's got!"
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