In 2011, Fox News announced that a new guest would appear weekly on “Fox & Friends,” its chummy morning show. “Bold, brash, and never bashful,” a network ad declared. “The Donald now makes his voice loud and clear, every Monday on Fox.”

It was the beginning of a beautiful friendship.

Seven years later, the symbiosis between Donald J. Trump and his favorite cable network has only deepened. Fox News, whose commentators resolutely defend the president’s agenda, has seen ratings and revenues rise. President Trump views the network as a convenient safe space where he can express himself with little criticism from eager-to-please hosts.

Now, the line between the network’s studios and Mr. Trump’s White House is blurring further. Bill Shine, a former Fox News co-president who helped create the look and feel of the channel’s conservative programming, is expected to be hired as the president’s new deputy chief of staff, overseeing communications.

He was recommended to Mr. Trump by a mutual friend: Sean Hannity, the Fox News star who has become a confidant of the president and promoter of the administration’s message to his average nightly audience of about 3.4 million viewers, the biggest in cable news.

Presidents have long cultivated influencers in the media: Lyndon B. Johnson sought Walter Lippmann’s policy advice, and John F. Kennedy was family friends with Benjamin Bradlee, who covered his administration for Newsweek (and occasionally enjoyed flights on the president’s plane). Barack Obama held dinners with political columnists and had his preferred interlocutors: Steve Kroft of “60 Minutes” interviewed him 17 times.

The Trump-Fox connection, though, extends beyond friendship and flattery to outright advocacy. The president is the beneficiary of a sustained three-hour block of aggressive prime time punditry, which has amplified his unfounded claims and given ballast to his attacks on the news media as the “enemy of the American people.”

Commentators like Mr. Hannity both parrot and help shape the president’s narratives. In Mr. Hannity’s case, he has denounced the investigation by the special counsel, Robert S. Mueller III, as part of a “deep state” conspiracy carried out by a “crime family.” Laura Ingraham recently described the facilities holding children separated from their migrant parents as “essentially summer camps.” Talking points from “Fox & Friends” are a staple of the president’s Twitter feed.

The prime-time rallying cry of “fake news,” in particular, has led some veteran journalists in the Fox newsroom to publicly chastise their opinion-side counterparts: Chris Wallace, the host of “Fox News Sunday,” recently dinged his network’s commentators for “bashing the media,” calling it “bad form.” But the attacks have apparently pleased the president, who as of Sunday had granted 23 interviews to Fox News and Fox Business Network — roughly two-thirds of his television interviews since Inauguration Day.

The coziness has angered critics who label Fox News “state TV,” a sobriquet — lobbed by rival TV news leaders like Jeff Zucker of CNN and Andrew Lack of NBC — that Fox News executives emphatically reject.

Several former Fox News employees said they did not recall the channel so rigorously supporting a sitting president’s agenda. “It’s fair to say that there’s a relationship that’s been forged,” said Eric Bolling, a former co-host of “The Five” who left Fox News last year after denying allegations that he had sent inappropriate pictures to colleagues.

Fox News’s Trumpward tilt comes as the president is enjoying some of his highest approval ratings since he was sworn in. At the same time, Mr. Mueller’s approval ratings have fallen to a low point.

Mr. Trump’s preference for Fox News pundits has also meant fewer opportunities for him to be questioned by journalists who do not share his ideology — including reporters at Fox News. The network’s chief political anchor, Bret Baier, was shut out for nearly 18 months before Mr. Trump agreed to sit with him, and Mr. Wallace has not interviewed the president since he took office.

Ken LaCorte, who was the senior vice president of Fox News Digital before leaving in November 2016, said that Mr. Trump received more favorable coverage at the network “after he became the Republican nominee, and part of that, I think, is ratings driven.”

“I do see more news stories that are more Republican-leaning than I ever had,” said Mr. LaCorte, who also faulted CNN and MSNBC for what he derided as anti-Trump “resistance” punditry. “I’ve seen the shift in all the national media to harden their positions, and play more to their perceived audiences.”

The network pointed out that its commentary has always skewed to the right and has been generally supportive of Republican leaders, and noted that Ms. Ingraham and Tucker Carlson, another prime-time host, occasionally knock Mr. Trump for intemperate tweeting, or not taking a harder line on immigration.

Mr. Shine is also not the first Fox News figure to join a White House in a high-ranking role: Tony Snow, the original host of “Fox News Sunday,” became George W. Bush’s press secretary in 2006.

There was a time when Fox News commentators were more willing to criticize Mr. Trump.

In July 2015, Mr. Trump, then a long-shot candidate, derided Senator John McCain’s captivity in Vietnam. “If Eric Holder had said this — Fox News, we’d be covering it 24-7,” Greg Gutfeld, co-host of “The Five,” said on the show. “We would be demanding resignations and investigations, which is why we need to hold Donald Trump to the same standards.”

Roger E. Ailes, the channel’s late chairman, said it was “disturbing” after Mr. Trump suggested that Megyn Kelly had asked tough questions during a primary-season debate because she was menstruating. And Bill O’Reilly, while still the No. 1 anchor on Fox News, challenged Mr. Trump over his sympathies for Vladimir Putin.

Ms. Kelly has since left Fox News for NBC, and Mr. O’Reilly was ousted after a sexual harassment scandal. They were replaced in prime time by Ms. Ingraham and Mr. Carlson, who frequently draw bigger audiences than their predecessors.

Those higher ratings have kept Fox News ahead of MSNBC and CNN in the Nielsen charts, and the network recently celebrated its 197th consecutive month — that’s 16 years, 5 months — as the most-watched cable news network in prime time and over the 24-hour broadcast day. It generates more than $1 billion in annual advertising revenue for Rupert Murdoch’s media empire.

People inside Fox News say that with Mr. Ailes out of the picture, the network’s producers and hosts have more leeway. These days they intuit what their viewers want and adjust their programming accordingly.

Ralph Peters, a retired lieutenant colonel in the United States Army with an expertise in United States-Russia relations, recently quit his job as a Fox News analyst, calling the network a “propaganda machine.” In an interview, he said that during his final months at the network, “I was asked ever less frequently to speak about anything that touched Trump and Russia.”

“Nobody at Fox ever tried to put words in my mouth,” Colonel Peters said. “Nobody ever said, ‘You can’t say that.’ They just didn’t ask me to do those segments. There’s not some deep dark cabal. Organizations, whether it’s The New York Times or Fox News, grow a collective sense of what the bosses want, what direction the organization is supposed to go.”

Asked if he considered Fox News “state TV,” Mr. Peters said that was a stretch. “They are not controlled by the state,” he said. “Fox is influenced by an administration.” (The network said Mr. Peters “is entitled to his opinion despite the fact that he’s choosing to use it as a weapon in order to gain attention.”)

Back in 2011, the decision to bring Mr. Trump into the “Fox & Friends” fold was a ratings-driven move: His occasional guest appearances had proved so popular that executives offered him a regular slot. Disdain for the Obama White House was a bonding point for the co-hosts and Mr. Trump, who shared his false theories about Mr. Obama’s place of birth.

Mr. Ailes, who died in 2017, saw the allure of his network’s new guest. Once, at a meeting with senior producers, according to a person in attendance, the executive said Mr. Trump appealed to Fox News viewers because he lived his life in a manner that many of them imagined they would, too — if they were rich.

At the time, Mr. Trump was a white male in his 60s, squarely in the network’s core audience, and his unfussy patriotism and keen sense of aggrievement made him a natural fit for the Fox News aesthetic. And when it came time for President Trump to build out his administration, he knew where to turn.

At least three Fox personalities — Mr. Carlson, Ms. Ingraham and Kimberly Guilfoyle — were considered as potential White House press secretaries. Jeanine Pirro, whose weekend show has ballooned in viewership since Mr. Trump took office, interviewed to be a deputy attorney general. Heather Nauert, after a decade at Fox News, became a State Department spokeswoman.

Since his inauguration, the president has tweeted about Fox News or Fox Business more than 220 times. His son Donald J. Trump Jr. is dating Ms. Guilfoyle. (Fox News said Ms. Guilfoyle, who co-hosts “The Five,” is required to disclose the relationship when discussing the Trump Organization on-air.) One morning in June, Mr. Trump surprised advisers by leaving his residence for a spur-of-the-moment “Fox & Friends” interview on the White House lawn, forcing the host, Steve Doocy, to scramble for questions.

Mr. Shine’s likely move to the White House did not surprise network veterans. A Long Island native and son of a New York City police officer, Mr. Shine had a hand in designing Fox News programming for two decades. Deeply loyal to Mr. Ailes, he was forced out of the network last May for his handling of sexual harassment scandals. He and Mr. Hannity are close, often traveling together with their families.

“He has an uncanny way of telling you ‘no,’ where you don’t feel bad about telling you ‘no,’” said Mr. Bolling, who is now a host on the conservative streaming network CRTV. “If he can tell the president ‘no’ when he needs to be told ‘no,’ that’s fantastic.”

Mr. Peters called Mr. Shine “a brilliant choice” for the White House. “He doesn’t spend all his day reading Milton and Dryden, but he’s very perceptive,” he said.

Ted Koppel, the former anchor of “Nightline,” said that Mr. Trump’s relationship with Fox News was “clearly a little bit different” from the interplay between media organizations and past presidents.

But he also urged some perspective, noting that CNN and other cable networks dedicated hundreds of hours of airtime to Trump rallies during the 2016 campaign.

“There weren’t a lot of our colleagues who covered ourselves with glory at that time,” Mr. Koppel said. “They were just so happy to get him on.”