Donald Trump on Fox News.

The mounting problem Donald Trump poses to Republicans is also a mounting problem for the country’s most powerful conservative media mogul: Rupert Murdoch. This morning’s New York Times gives front-page treatment to the billionaire grudge match that has become a major story line in this year’s (already) fractious GOP primary. The piece by political reporters Amy Chozick and Ashley Parker chronicles Murdoch’s intensifying efforts over the past week to blunt Trump’s surge to the top of the crowded GOP field. In recent days, Murdoch has tweeted that Trump is “wrong” and “embarrassing.” On Sunday, the New York Post mocked Trump on the cover with the headline “DON VOYAGE” and featured him marooned on a life raft being circled by a shark. The same day, The Wall Street Journal ran a scathing editorial that labeled Trump a “catastrophe.”

One reason Murdoch is taking to social media and deploying his publishing properties to attack Trump may be the simple fact that he hasn’t been able to control his most powerful media organ: Fox News. According to sources, Murdoch has tried — and failed — to rein in Fox News Chairman and CEO Roger Ailes, who, insiders say, is pushing Fox to defend Trump’s most outlandish comments. This week, Ailes told his senior executives during a meeting that Murdoch recently called him and asked if Fox could “back off the Trump coverage,” a source told me. Ailes is said to have boasted to his executives that he told Murdoch he was covering Trump “the way he wanted to.” The implication was that he wasn’t going to budge.

Nathaniel Brown, a Murdoch spokesperson, declined to comment. Fox News spokeswoman Irena Briganti did not return a call seeking comment.

It’s understandable that Murdoch would be frustrated. Fox News has been a ringleader of the Trump circus. Shortly after Trump jumped into the race, he had a “2-to-3 hour” private lunch with Ailes, sources told me. Last month, Fox gave Trump more airtime than any other candidate. And, according to sources, the channel’s personalities are taking an active role in aiding Trump, both on- and off-camera. One source explained that Ailes has instructed The Five co-host Eric Bolling to defend Trump on air. A review of Bolling’s comments shows that over the past week, he’s gone to bat for Trump numerous times. Last Friday, for example, Bolling complained that conservatives shouldn’t be criticizing the real-estate mogul. “There’s a problem in America, and it’s not Donald Trump,” Bolling declared. He continued to make pro-Trump arguments on Monday and Tuesday’s shows. Another Trump ally is Fox political analyst and pollster Pat Caddell. According to a source with direct knowledge, Caddell has been speaking to Trump “almost every day” about his campaign. “Everything coming out of Trump’s mouth sounds like Pat,” the source said. This morning, Fox & Friends — a show that is used by Ailes to inject his point of view into debates — ran a fawning interview with Trump. At one point in the conversation, co-host Steve Doocy gushed that “someone told me yesterday Donald Trump is like a Navy SEAL.” For his part, Trump has been grateful for the Fox & Friends support. Yesterday, at a campaign event in South Carolina where he gave out Lindsey Graham’s personal cell-phone number, Trump heaped praise on Fox & Friends’ Doocy, Brian Kilmeade, and Elisabeth Hasselbeck. “They’re great people,” he said.

Murdoch’s public and private attempts to temper Ailes make Sunday’s Wall Street Journal editorial all the more fascinating. The piece — which carries no mention of Fox — excoriated the conservative media “apologists” that have been backing Trump. “Too many have adopted the view that there can be no adversary to their right,” the Journal said. “This was mainly a left-wing affliction in the last century as many liberals refused to condemn Communists. But today many on the right seem willing to indulge any populist outburst no matter how divorced from reality or insulting to most Americans. If Donald Trump becomes the voice of conservatives, conservatism will implode along with him.”

Inside Fox News, the Journal editorial is clearly seen by some as a message to Ailes. It seems doubtful, however, that he is listening. “Roger claims not to care,” an insider said.