Donald Trump is going full tilt against Megyn Kelly again, on Twitter and in the press and according to New York Magazine’s Gabriel Sherman, Fox CEO Roger Ailes is starting to sweat.

On CNN yesterday, Trump followed up his demand that Kelly be removed from the upcoming Fox News Republican candidates’ debate with insults and threats – including a not-so-veiled threat to spill the beans about some dark secret she may have.

Trump told Wolf Blitzer that he’ll “probably” take part in the debate. But moments later, he threatened not to:

TRUMP: I’m not a fan of Megyn Kelly. I don’t like her. She probably doesn’t like me and that’s OK but she’d better be fair. I’d like to go to the debate. I enjoyed the debates. I’ve done well in the debates. Every single poll has said I’ve won every debate. But we’re gonna see what happens. Gonna be exciting.

“Nothing’s 100%” on whether he’ll be there, Trump said. “If I think I’m gonna be treated unfairly, I’ll do something else.”

“I don’t think she can treat me fairly, actually,” Trump added. “I think she’s very biased and I don’t think she can treat me fairly but that doesn’t mean I don’t do the debate. I like doing the debates. I’ve won every single debate according to every poll.”

Trump also threw in the dig, “I might be the best thing that ever happened to her. Whoever even heard of her before the last debate?” Probably millions, Donald. Kelly was profiled in The New York Times and Variety, appeared on Jay Leno’s Tonight Show and Late Night with Seth Meyers and was repeatedly skewered by Jon Stewart, all before her famous debate confrontation with Trump on August 6. That’s not counting her little prime time show on Fox News five nights a week.

Trump also said menacingly on CNN, “I’m not a big fan of hers. Maybe I know too much about her.”

Blitzer did not press for more details.

Fox fired back at Trump, saying, “Sooner or later Donald Trump, even if he’s president, is going to have to learn that he doesn’t get to pick the journalists — we’re very surprised he’s willing to show that much fear about being questioned by Megyn Kelly.”

But Trump is not backing down. Tonight, he went after Kelly again on Twitter:

And Sherman sees weakness behind Fox’s bluster. He writes:

The timid response – by Ailesian standards – is more evidence that the Fox chief is struggling to draft a playbook to deal with Trump. According to a Fox source, Ailes’s senior executives convened an emergency conference call on Sunday to discuss Fox’s Trump strategy. Two more sources told me that Ailes is becoming increasingly worried about leaks from inside Fox. He’s tasked his lawyer Peter Johnson Jr. with running an investigation to ferret out sources.

As I previously wrote, I think it’s highly unlikely Trump will skip the debate. But whether or not Megyn Kelly pulls her punches as a moderator is another question entirely.

Stay tuned!

Trump’s January 25th CNN interview with Wolf Blitzer is below. The portion about the Fox debate starts at about 9:55.