Why did Fox News president Roger Ailes fire his top lieutenant? The sudden ousting of PR chief Brian Lewis, who had pioneered the channel’s aggressive public relations strategy since its founding in 1996, inspired plenty of speculation and spin — some of it from the network’s on-air talent — about Lewis’s reputation at the channel, Fox’s vague claims of “financial irregularities,” and what the channel called “multiple, material and significant breaches of [Lewis’s] employment contract.”

But it was suspicions about Lewis’ relationship with writer Gabriel Sherman that sent boss Roger Ailes over the edge, an insider source at 21st Century Fox confirmed. “The financial stuff would have been a slap on the wrist if there weren’t a sense that [Lewis] was talking outside the company,” the source told Gawker, referring to Sherman and his upcoming inside account of Fox News, The Loudest Voice in the Room. “Ailes felt: This guy fucked me, and I am going to fuck him harder.”

Lewis had long served as a liaison between Ailes and non-Fox media, including the (authorized) Ailes biographer Zev Chafets, so dealing with people like Sherman was a central part of his job. But Sherman, unlike Chafets, has criticized Ailes and his channel, and publicly feuded with Ailes’s wife, who cancelled Sherman’s subscription to a upstate New York newspaper Ailes bought in 2008. And Lewis was placed highly enough that Sherman’s biggest revelations could, in theory, be attributed to him.

Lewis’s relationship with Sherman, according to the 21st Century Fox source, gave his colleagues, including Irena Briganti, an opening to push Lewis out. “It was Irena and others who worked for him that divulged a lot of this stuff to Ailes—that he was talking to Sherman and the financial stuff,” the source said.

That “financial stuff,” we are told, involves allegations that Lewis expensed vacations and other leisure activities that weren’t strictly work-related.

The source added, referring to Briganti’s penchant for unnecessary aggression: “Irena is now trying to tell people that Brian forced her to be the pit bull with reporters so that he could play the good guy. Everyone there was terrified of him. All the ugliness they were putting out was manifested on the inside.”

One of the vectors of that “ugliness” is Greta van Susteren’s blog, which last week attempted to shrug off news of Lewis’s departure by claiming, laughably, that he was essentially a nobody—“Frankly, I don’t think I could pick Brian out of a line up!” van Susteren wrote. She may not have seen Lewis around the office much, working as she does out of the network’s Washington bureau. But our source said she certainly knew who he was, having engaged in a lengthy internal battle with him over his efforts to replace her with Megyn Kelly. “That’s such bullshit,” our source said. “They hated each other, because Brian was always pushing for Megyn Kelly to take over her timeslot. She knows who he is.” (Indeed, Kelly will reportedly take Sean Hannity’s slot soon, leaving observers to wonder whether Hannity will take over Van Susteren’s in turn.)

It remains unclear precisely what kind of relationship Lewis had with Sherman. But his job certainly involved attempting to manage a book that would, for better or worse, have a role in shaping Ailes’ legacy. And Sherman has certainly let loose a string of scoops on Fox News’ internal struggles over the past two years. Lewis could have been feeding them to Sherman, or Ailes’ legendary paranoia could have set in. The mere appearance of betrayal, regardless of actual proof, might have been enough for Ailes to cut ties with Lewis.

That’s not to say there was no proof. Shortly after the news of Lewis’s firing surfaced, Sherman recounted an exchange in which Lewis called anchor Bill O’Reilly a “chucklehead” for being photographed next to a woman’s exposed breasts.

Nor is Lewis the first News Corporation (now 21st Century Fox) image specialist to be shown the door — by force or encouragement — over a bungled book project. Rupert Murdoch flack Gary Ginsberg quietly left the company in 2009 over the fallout of media critic Michael Wolff’s less-than-positive biography of the aging Australian, which claimed that Murdoch is routinely ashamed of Fox News. (Ginsberg, much like Lewis, negotiated the ground rules between Murdoch and Wolff.)

Lewis declined to comment for the record. Sherman was not available to comment.

Update: A 21st Century Fox spokesman sent the following email in response.

Brian Lewis was terminated for cause on July 25 for a multitude of infractions. Irena Briganti and the entire staff of the FOX News PR department had absolutely nothing to do with his termination and had no role in the investigation or the current press surrounding his termination. Anything that suggests the contrary is nothing more than vicious gossip by sources without first-hand knowledge of the situation.

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