But as Fox vows to cover impeachment in a rigorous and fair-minded way in its news programming, if not opinion shows, the network is becoming a kind of Rorschach test for cracks in the president’s media firewall. The calculus is simple: If Fox starts allowing more anti-Trump conservatives to voice concerns about the president’s behavior, it clears the way for conservative House members and senators to express doubts of their own without having to worry about a conservative media backlash.

Joe Walsh, a former Republican congressman and radio host now running a long-shot primary bid against Trump, told POLITICO that current members look to Fox News for signs of what’s acceptable conservative dialogue.

“They don’t fear Trump. They fear his voters,” Walsh said. “They know his voters digest Fox News every day, so they toe the line with what Fox News is doing [and] put out crap about the ‘deep state’ and all this other stuff they really don’t believe in.”

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So far, Fox News is hewing closely to the White House line. Pro-Trump voices dominate the conversation, especially in the morning and evening hours, though several of the network’s anchors and analysts have scrutinized claims by the president and his allies that would likely go unchecked — or get endorsed by — by supportive hosts and guests.

For instance, “Fox News Sunday" host Chris Wallace challenged White House adviser Stephen Miller’s baseless accusation that the whistleblower who sparked the Ukraine scandal is a “deep state operative.” At one point, Wallace dubbed Miller’s evasive answers “an exercise in obfuscation.”

But Miller found a more receptive audience Tuesday night on Fox Business, telling host Lou Dobbs that the “fake whistleblower” is part of a plot to “overthrow” the president. “The deep state,” Dobbs responded, is “not only entrenched, but expanding and increasingly powerful.”

Such assertions, often reinforced with Trump tweets and online messaging, make the jobs of Fox’s news reporters more difficult.

“The right-wing opinion hosts are essentially selling snake oil and clickbait with nonsense to support the president,” said Carl Cameron, who spent two decades at Fox News and recently launched progressive news site Front Page Live.

In an interview with POLITICO, Cameron praised Fox news anchors such as Wallace, Shep Smith and Bret Baier and said that journalists at the network are “constantly battling the falsehoods that the right-wing opinion hosts are throwing out there.”

Relatively few Republicans have offered criticism of the president surrounding impeachment, but they’ve often struggled to get their views acknowledged by Fox. Illinois Rep Adam Kinzinger stood out in calling Trump’s invoking of the Civil War to describe his plight as “beyond repugnant.” Kinzinger’s comment was covered on Baier’s 6 p.m. newscast, though not on Fox News’s prime-time shows.

Walsh suggests conservative critics of Trump, like himself, aren’t getting enough airtime on the network. The former congressman has called for impeaching Trump this past week on MSNBC and CNN, but hasn’t scored an invite from Fox News. He last appeared on Fox Business in August in a contentious segment in which he and host Stuart Varney sparred over whether Trump has ever lied.

“I do believe more and more Republicans deep down are tired of this guy and are tired of his bullshit,” added Walsh. “They’re just afraid to publicly come out and say that.”

That sentiment echoes former Sen. Jeff Flake’s contention that at least 35 Republican Senators would vote to impeach Trump if they could do so privately.

Another Republican primary challenger, Mark Sanford, hasn’t expressed support for impeachment but said he wants the allegations against Trump investigated. Sanford has appeared on MSNBC and CNN since the Ukraine scandal broke, but not Fox News. He last appeared on the network on Sept. 11.

Once a paid Fox News contributor, the former South Carolina governor and congressman said he doesn’t expect such a role again given his criticism of Trump and now exists in “something of a media no-man’s land.” In an interview, Sanford struck traditional Republican notes around debts, deficits and free-market competition, and lamented that some policy views coming from the White House and echoed by Fox hosts and others are “anything but conservative.”

Trump presumably isn’t concerned about having conservative policy debates on Fox News as Democrats pursue an impeach inquiry. He tends to promote praise for him and his administration, and on Sunday amplified a portion of on-air remarks from a supporter, Pastor Robert Jeffress, to warn of a “Civil War-like fracture” if he’s removed from office.

The president also aggressively pushes back against perceived slights. He fired off more than 20 tweets and retweets on Sunday featuring criticism of Fox News reporter Ed Henry after he asked commentator Mark Levin if he was OK with Trump wanting Ukraine’s president “to dig up dirt” on the Bidens.

“Your question is not honest,” said Levin, a prominent conservative radio host who also has a weekend show on Fox News. Levin proceeded to accuse the media of lying, with “Fox & Friends” co-host Pete Hegseth, a reliable Trump booster, adding “the press is entirely uninterested in the other side.”

The intramural spat was one of several to play out on air. Conservative radio host Jordan Sekulow said Monday morning on Fox News that Wallace’s questioning of Miller was “unfair” because the White House adviser isn’t an attorney. Sekulow’s father, Jay Sekulow, is Trump’s lawyer and appeared that night on “Hannity,” along with the president’s most visible attorney: Rudy Giuliani.

Giuliani has accused Biden of corruption, suggesting the former vice president sought the removal of a Ukrainian prosecutor to benefit his son Hunter’s business interests in the country; there is no evidence to support Giuliani’s claim.

“How much in the tank and how corrupt this media has become,” Giuliani said. “They have corruption staring them in the face and they close their eyes to it and then they make up charges against President Trump that aren’t true.”

The next morning on “Fox & Friends,” co-host Brian Kilmeade said that despite some “sensationalistic headlines” over impeachment “there’s almost no there there.”

Later that hour, senior judicial analyst Anthony Napolitano dismissed the allegations against Biden. “Prosecutors in Ukraine and even prosecutors here in the United States say there’s no there there,” he said.

Napolitano, a libertarian conservative, also diverged last week from the pro-Trump stable, suggesting to anchor Shep Smith that Trump committed a crime when he urged Ukraine’s president to investigate the Bidens. Joe diGenova, a Trump-supporting lawyer who has made dozens of appearances this year on Fox News and Fox Business, called Napolitano a “fool” hours later on “Tucker Carlson Tonight.”

Smith, who hosts the 3 p.m. news hour, said the next day that it was “repugnant” for diGenova, a “partisan” guest on an “opinion” show, to attack a Fox News colleague for offering legal assessments. Carlson swung back, saying it “doesn’t seem honest” for a host to assert Napolitano’s view isn’t an opinion.

DiGenova also disputed Wallace’s report Sunday that he and his wife, Victoria Toensing, were “working off the books” with Giuliani “to get oppo research on Biden.”

In an interview Monday on WBAL, diGenova said Wallace’s report was “absolutely false.” DiGenova said Giuliani asked him and Toensing to represent Ukrainian “whistleblowers,” but said the trip to Ukraine was “canceled” and the pair “were never representing.” Wallace stood by his reporting.

The on-air fissures haven’t gone unnoticed across the cable dial. Rick Wilson, a Republican operative and Trump critic, said Monday on MSNBC that Wallace and Smith “must be pretty lonely over at Fox these days, because the rest of the network is blasting out deep state conspiracy theory propaganda 24/7 right now.”

And on Wednesday morning, MSNBC host Joe Scarborough mocked Rivera's description of Hannity as a bulwark between Trump and impeachment.

“Was that a compliment?” Scarborough asked. “You know, if Al Capone had had somebody like you, Sean. ... I mean, c’mon are you kidding me?”