The perceived favoritism by Roger Ailes, left, and Fox News toward Donald Trump, right, has prompted establishment conservatives to lash out at the network they once considered a beacon. (Charles Sykes/Invision/AP; Carlo Allegri/Reuters)

Ever since Fox News debuted in 1996, liberals and moderates have been grinding their teeth over its frankly conservative commentary and right-leaning news agenda. Fox itself has never officially branded itself a conservative network, although its famous slogan — “Fair and Balanced” — was a subtle rebuke to what its co-founders, Rupert Murdoch and Roger Ailes, saw as the mainstream media’s liberal bias.

But in the Age of Trump, Fox is drawing disapproving, even scathing, critiques from an unlikely source: conservatives.

There was syndicated talk­radio host Mark Levin, who disparaged Fox as “a Donald Trump Super PAC” and “not a news channel” after two Fox hosts gave serious consideration to a National Enquirer story linking Ted Cruz’s father to the Kennedy assassination. There was Glenn Beck, a Fox exile, who accused the network of using lighting and camera tricks to make Trump look more “presidential” during interviews.

Recently, though, the fiercest criticism is coming from voices that are traditionally more measured — notably from the “Never Trump” movement of establishment conservatives, who fault the network for boosting the mogul’s candidacy.

Fox’s powerful voice “is killing the conservative movement,” wrote David French in the National Review last week. The network, he wrote, “has constructed a big, beautiful and lucrative gated community — a comfortable conservative cocoon” in which conservatives “persuade each other of the rightness of their ideas. . . But they never get a chance to preach to the unconverted,” dooming the party to losing the popular vote in presidential elections.

Glenn Beck has criticized Fox’s coverage and even (gasp!) praised CNN as the only network that “didn’t have a horse in the race.” (John Sommers II/Reuters)

French’s essay echoed another National Review piece last month by Matthew Sheffield, who noted that Fox has little reach beyond a relatively small segment of conservatives. “The seeming success of Fox News and talk radio has made many conservatives think they now have a massive media empire,” he concluded. “In truth, they have constructed an intellectual ghetto that no one else wants to visit.”

National Review’s animosity toward Fox may be new, but the venerable conservative journal founded by William F. Buckley Jr. hasn’t been shy about its dislike for Trump. In January, it published a special issue under the title “Against Trump,” in which 22 prominent conservative figures wrote essays outlining their opposition to the candidate.

The magazine’s take on Fox’s “echo chamber” gets a modified amen from Bill Kristol, the editor of the conservative Weekly Standard and a former commentator on Fox. “The left was more dis­advantaged by living in their [liberal media] echo chamber in the 1970s and ’80s,” says Kristol, a Trump opponent, in an email. “They. . . were astonished when Reagan won twice and then Bush. Then conservative media grew up, and now there’s a conservative echo chamber, which it can be easy and comfortable to fall into.”

Lesser-known figures have joined the brawl, too. Steve Deace, a talk-show host, ripped Fox for its alleged pro-Trump tilt, writing in Conservative Review in April: “Here lies Fox News, formerly known as the definitive standard-bearer for conservative media. Born: 1996. Died: 2016. Cause of death: Shilling for Donald Trump.”

The notion that Fox has been biased against conservative candidates carries its own rich irony. One of Fox’s long-running themes, almost a part of its founding charter, has been its attacks on liberal media bias — a claim repeated endlessly by prime-time hosts Bill O’Reilly and Sean Hannity, as well as by a parade of Republican politicians — Sarah Palin, Mike Huckabee, Newt Gingrich, Rick Santorum — hired as commentators and provocateurs.

The irony within the irony is that Trump himself has criticized Fox — or at least one of its most popular hosts, Megyn Kelly: During the campaign, he reacted in a vulgar manner to Kelly’s question about his disrespectful comments about women during the first Republican debate last year and later boycotted a Fox­sponsored debate in January. (They seemed to make up in May during a prime-time interview special hosted by Kelly).

On the other hand, Trump has maintained friendly, and mutually beneficial, relations with other parts of FoxWorld. Ailes — now deposed as Fox’s chairman because of allegations of rampant sexual harrassment — is reportedly an informal adviser to his campaign. And the candidate has appeared dozens of times on “Fox and Friends” as well as the programs of O’Reilly and Hannity, who has lately lashed out at Beck and the “Never Trump” crowd for supposedly enabling a Hillary Clinton victory. (“She wins, I’m blaming all of you,” Hannity thundered on his radio show last week. Beck, in return, doubled down with an indirect slam on Fox when he praised CNN’s campaign coverage during an appearance on its “Reliable Sources” show Sunday: “I know a lot of conservatives that said you guys were the only ones we could watch because you didn’t have a horse in the race. So you just presented the facts the way they were.”)

The conservative criticism of Fox seems to reflect two intertwined trends: the factionalization of the Republican Party into populist, insurgent and establishment camps, and the flowering of alternative conservative news sources. While it remains the most prosperous and influential news organization among conservatives, Fox’s dominance has been challenged in recent years by such new operations as the Trump-supporting Breitbart News, Beck’s TheBlaze, multiple talk-radio programs and Beltway-based websites the Daily Caller and Washington Free Beacon.

For its part, Fox rejects the complaints from the right, much as it has rejected them from the left.

“As a news organization, we don’t cater to any political party, and the fact that we’ve been criticized from across the political spectrum proves that we are doing our job in reporting the news accurately and fairly,” said Bill Shine, who became Fox’s co-president after Ailes was forced to resign in July. “Considering we’ve been number one all summer in basic cable and we are having our highest ratings ever, I think viewers are pretty happy with the product we’ve produced.”

Conservative gripes about Fox demonstrate how the network is caught betwixt and between the Republican Party’s own ideological crossfire, says Dan Cassino, a political science professor at Fairleigh Dickinson University and the author of “Fox News and American Politics: How One Channel Shapes American Politics and Society.

Spanning the gaps among Trump’s populist/nativist wing, Beck’s hard-right and the GOP’s establishment or “chamber of commerce” faction, he said, could prove to be a long-term threat to the network. “It’s an economic issue for Fox,” he said. “They can’t afford to alienate” one group at the expense of the other, or ratings and ad revenues will fall.

The task became considerably harder, Cassino argues, without Ailes. Fox was largely a reflection of its 76-year-old former chief executive, a veteran Republican political operative who hired Fox’s stars and shaped what they would talk about each day. His particular genius, he said, was in identifying issues broadly acceptable to the conservative faithful — the Benghazi terrorist attacks, the “Fast and Furious” gun-running scandal, the so-called “war on Christmas” — even as these issues were ignored by the rest of the news media.

“Finding the right issues and the right terminology to talk about them every day isn’t easy,” no matter who the next president may be, he said. “Without Roger Ailes, I’m not sure they can do it.”