The other day, on the Fox News show, The Five, host Greg Gutfeld got real.

"On any given day we have tension over this candidate," Gutfeld said of Donald Trump, the GOP presidential front-runner. "You can look at this network where we are having issues within a family of anchors over this stuff. You can look at the party. Every area where there is conservatism, there is strife. I just remember the good old days when we could unite over a hatred of Obama."

Ahhh, the good old days. When Fox News conservatives spoke in near united voices for Republicans and against Democrats. Those good old days ended back in August, when Fox’s star anchor, Megyn Kelly, opened the very first Republican presidential debate by challenging front-runner Donald Trump.

"You’ve called women you don’t like fat pigs, dogs, slobs, and disgusting animals," Kelly began, in an instant-classic debate moment.

The next day, Trump trashed Kelly on CNN. And most famously, he seemed to make reference to her menstrual cycle. "You could see there was blood coming out of her eyes, blood coming out of wherever," Trump said.

Thus began a feud that has escalated into a compelling storyline of the national campaign. Trump boycotted a debate because Kelly was moderating. He has regularly bad-mouthed her on Twitter and at rallies. And Fox News has used official statements to push back on Trump -- once mocking him for being scared of Kelly, and saying he'd therefore be afraid to meet with Vladimir Putin. 

Much has been made of how Trump has upended the Republican party with his unorthodox candidacy. But as the presidential race moves toward the New York Primary, there’s another institution -- this one right on Sixth Avenue in the heart of midtown Manhattan -- where Trump is causing continued turmoil.

Fox News is still the top-rated cable news outlet. In fact, its ratings this election season are, as Trump would say, huge. But its position as the most powerful voice in conservative media is gravely and perhaps permanently weakened.

"The civil war you see going on within the conservative media bubble is a mirror of what you see happening in the Republican party," said Gabriel Sherman, a New York magazine editor and author of the best-selling book, "The Loudest Voice in The Room," about Fox News' chief Roger Ailes. "And these fault lines have cracked open and Donald Trump has been kind of the seismic force that caused this earthquake."

Network hosts have picked sides. Sean Hannity is largely sympathetic to Trump. Brett Baier often has guests on his show who are anti-Trump. And Bill O’Reilly, the ratings king from the network's old guard, has known Trump for years and gone up to the Bronx to watch the Yankees with him. O’Reilly reportedly triggered a feud with Kelly, the new star, when he failed to challenge Trump on the comments about her.

In previous political cycles, Sherman said, Ailes' marching orders meant personalities talked in lock step. No longer. Now, as Gutfield affirmed live on the air, things at Fox are awkward -- all because of Trump.

Part of the awkwardness is due to the fact that this is a family feud, a distinctly New York fight featuring Kelly, of the Upper West Side, versus Trump, of Fifth Avenue’s Trump Tower. Kelly, Trump and Fox’s executives are all members of the same club of Manhattan elite from media, real estate, finance and politics.

"Every town, every locale has a group of people who talk to each other," said Hank Sheinkopf, a long-time New York political consultant and regular guest on Fox News. "Trump has been an established part of the New York elite that he is now wreaking havoc on."

The candidate is not only of their world, he is also a creation of it. During President Obama's first term Fox gave Trump countless hours of airtime to float the conspiracy theory that Obama wasn't born in the country. Trump even had a weekly call-in segment on the popular morning show, Fox & Friends. 

"Fox & Friends gave Trump a national platform to push the birther conspiracy into the mainstream," Sherman said. "He was a ratings magnet for the network. And I think that gave him a lot of leverage because he knew he could challenge the network."

So once Kelly turned on Trump at the debate, he relied on the loyalty of the viewers to go after Fox -- even if it meant a split with his friend and fellow New York media titan, Ailes.

"Roger Ailes sort of found himself torn between his star anchor, who has become in many ways the face of Fox News, and his long-time friend Donald Trump, who just happens to be the leading presidential candidate," Sherman said. "And in this kind of three-way triangle there is sort of a tug of war for the heart and soul of Fox News."

On one hand, war has been good for the cable news channel. Fox-versus-Trump is covered by Fox and perpetuated by Trump. Controversies beget ratings -- and Fox News ratings in prime time are up 40 percent over last year.

But while Trump has brought riches, he hasn’t brought all smiles to the network. Hosts who don’t toe the Trump line face a barrage of angry, vicious tweets from pro-Trump viewers. Kelly herself has faced death threats.

And the battle lines are evident on conservative talk radio.

"You’re seeing this sort of civil war in this Republican Primary that extends not just to Republican voters but within conservative media outlets," said Rich Zeoli, who hosts a conservative talk show on 1210 WPHT in Philadelphia. For the first time ever in his career, callers to Zeoli's show are actually complaining about Fox News being biased against them.

"I hear more and more of them say they’re tuning into CNN over Fox News because they feel that lately CNN has been more fair to Donald Trump," Zeoli said. 

Fox has become the establishment that Trump rails against. It is lumped in with the same media Trump supporters are suspicious of. Competition from hard-right upstart news organizations, like Breitbart, are also helping to break the Fox monopoly. Even Rush Limbaugh, the preeminent conservative radio show host, said as much to his listeners: "I’m here to tell you Fox News is not considered the conservative network that it used to be."

Beyond his profound impact on the country’s politics, this may be the most enduring effect of Trump's candidacy.