In the closing minutes of his podcast, the right-wing provocateur Dan Bongino made a promise. Joining the F.B.I. as its deputy director, he acknowledged, would require a stark change in approach after years of making his name as a pugilistic pundit.

“I have to stay out of the political space because it’s the right thing to do and it’s the rules,” he said during his last episode on Friday. He added, “I’m not going there to be some partisan.”

His arrival on Monday as the F.B.I.’s second in command will test that promise, cementing a major shift at the nation’s premier law enforcement agency, where he will join its director, Kash Patel, in overseeing a bureau of about 38,000 people. It puts two staunch Trump loyalists in charge of an agency long known for its tradition of independence. Collectively, they have the least leadership experience of any pair overseeing the F.B.I. since its founding more than a century ago.

Already, Mr. Patel has raised eyebrows. He has reversed course on a pledge to install a veteran agent as his No. 2 and works out with a personal trainer inside the F.B.I. He has swiftly moved to restructure the bureau, pushing to decentralize the command structure and reassign many at its headquarters. He quickly established a ballooning presence for his F.B.I. director account on social media, shooting down a wobbly theory in the right-wing media, which prompted a slew of stories and some astonishment.

In selecting Mr. Bongino, whose experience in law enforcement dates from years ago when he served as a police officer and Secret Service agent, Mr. Patel is breaking from tradition and relying on someone who has little familiarity with the bureau’s inner workings. Indeed, the past five deputy directors had spent an average of more than 20 years in the bureau. Mr. Bongino, by contrast, has never been an F.B.I. agent.

Best known as a high-octane conservative commentator, Mr. Bongino began his podcast in 2015, catapulting him to right-wing stardom during the 2020 election. Like Mr. Patel and Mr. Trump, Mr. Bongino is from Queens, N.Y.

Mr. Bongino frequently shared his disdain for the F.B.I. on his podcast and radio show while praising Mr. Trump. In an emotional farewell episode, he recounted how President Trump reached out after Mr. Bongino had a cancerous tumor removed in 2020, shortly before the election. “President Trump called in the hospital; he was the president; Covid was going on,” he said, adding that the president asked whether Mr. Bongino needed anything. He responded, “I need you to save the country.”

Mr. Bongino will replace Robert C. Kissane, who had more than two decades of experience as an agent and had been serving as acting deputy director. Mr. Kissane is expected to return to New York.

Hours after Mr. Patel was sworn in last month, he signaled his intent to sharply restructure the bureau, ordering the relocation of 1,500 agents and personnel in the Washington region to field offices around the country. Internal documents show that he told several hundred agents on temporary duty to return to their home offices by the end of June, a potentially significant shift in ascending the ranks of the agency. Those temporary assignments to headquarters are critical to getting promoted, providing agents with deep insights into the bureau’s abilities and reach.

But Mr. Patel will be hard-pressed to attain his larger goal because of steep relocation costs.

Last week, Mr. Patel also altered the hierarchy of the F.B.I., which could, in effect, insulate top agents in the field from Mr. Bongino because they will no longer answer to the deputy director. Some former agents saw that as a positive development.

A series of ousters that was already underway before Mr. Patel took office has left a leadership vacuum atop the agency.

James Dennehy, the widely popular and veteran agent in charge of the New York field office, was among about a dozen senior executives who have been pushed out. Some were agents with decades of experience who would have offered critical institutional expertise to Mr. Patel and Mr. Bongino. Now Mr. Patel intends to replace some of them with another cadre of senior executives

On the same day that Mr. Dennehy was forced out, Mr. Patel circulated a video to his staff saying he had their backs.

Mr. Patel also removed the people who knew how to run the seventh floor, where the director and the deputy sit. His new executive secretary previously ran a concierge business. Mr. Wray’s executive secretary had worked for years at the F.B.I. and U.S. Customs and Border Protection.

Mr. Patel’s unconventional approach has left former agents and analysts to wonder if he is up to the job. In a videoconference with senior agents, he said that he would like the F.B.I. to partner with the Ultimate Fighting Championship, the popular mixed martial arts company, and that he was not big on meetings or wearing suits.

He has liberally used social media to promote the F.B.I. in what he has cast as an effort at transparency and highlighted the bureau’s role in immigration arrests. Former and current agents have joked privately that since Mr. Patel took over on Feb. 21., the agency has stopped being corrupt.

His handling of the job has also prompted former and current agents to question if Mr. Patel is in fact in charge or if the bureau is simply on autopilot. His predecessor, Christopher A. Wray, often asked, “Are you a plow horse or a show horse?”

On March 7, Mr. Patel attended the graduation of a new F.B.I. agent class in Quantico, Va., and dressed in camouflage to observe the bureau’s elite tactical team. He then flew to a U.F.C. fight in Las Vegas, where Mr. Patel has said he plans to divide his time. (The plan stands at odds with the administration’s policy of requiring all federal employees to be in the office five days a week.)

In a picture of the Las Vegas fight posted on social media, Mr. Patel is spotted ringside, next to Dana White, the U.F.C. president, and a manager, Ali Abdelaziz. Mr. Abdelaziz, a former informant for the New York Police Department and F.B.I., eventually fell under suspicion for lying. After traveling to Egypt in 2008, he failed a polygraph and the F.B.I. in New York severed its ties with him, according to Police Department documents. Mr. Abdelaziz proudly proclaims his relationship with Mr. Patel on social media, sharing Mr. Patel’s messages and posting a picture of himself at Mr. Patel’s confirmation hearing.

Mr. Patel has also drawn some praise elsewhere. In a moving speech at the State Department on March 6, he pledged to do everything in his power to free American hostages abroad. “This is a top priority,” he said.

He has also defended the F.B.I., a remarkable shift from his years taking shots at the agency.

Last week, Mr. Patel praised the bureau’s arrest of a Customs and Border Protection official in Detroit, describing it as part of the “F.B.I.’s renewed efforts to crack down on public corruption and deliver accountability for the American people.”

But F.B.I. agents had been investigating the case well before Mr. Patel became director. Indeed, the criminal complaint shows that agents learned in April 2024 about a potential scheme to defraud the Federal Emergency Management Agency.

In years past, Mr. Patel has repeatedly denounced the F.B.I.’s investigation into the Trump campaign’s ties to Russia known as Crossfire Hurricane.

Yet as director, he set the record straight about one F.B.I. operation in London that took place during the Russia investigation. The operation involved the use of a female undercover agent who had gone to London to meet with a former Trump foreign policy adviser. The right-wing news media seized on the detail, casting it as a so-called honey pot operation under investigation by Mr. Patel.

Mr. Patel quickly rebutted the claim on social media: “A female agent was falsely referenced in the media this week as part of an alleged whistleblower disclosure- she was NOT a honeypot.”

Mr. Patel was right. The operation had already been scrutinized years ago by the Justice Department’s inspector general and a special counsel who found no wrongdoing.

One right-wing news outlet called Mr. Patel’s pushback “rare and extraordinary.”