Washington (CNN) President Donald Trump sought to distance himself from the Justice Department official he just named as acting attorney general in the face of mounting criticism about the legality and propriety of his appointment.

"I don't know Matt Whitaker," Trump said of the new acting attorney general, saying he hired him because he had worked for since-dismissed Attorney General Jeff Sessions . "He was always extremely highly thought of, and he still is. But I didn't know Matt Whitaker. He worked for Attorney General Sessions."

The President's comments are at odds with the relationship Trump has forged with Whitaker in recent months, even as his opinion of Sessions continued to sour. Whitaker has been at the White House dozens of times, including in meetings with Trump, and the two have spoken by phone on several occasions, including on the day that Deputy Attorney General Rod Rosenstein was expected to be fired.

And in an October 11 interview on Fox News, Trump made clear he did, in fact, know Whitaker well.

"I can tell you Matt Whitaker's a great guy. I know Matt Whitaker," he said.

Whitaker was not hired as Sessions' chief of staff by virtue of any pre-existing relationship with Sessions, but instead because White House officials believed Whitaker's loyalties would lie at the White House and not with the beleaguered attorney general, sources said.

And over the last year, Whitaker has told friends about his growing relationship with Trump. The President knew that he had played football and the tall, brawny former US attorney fit the image Trump liked, according to people familiar with their conversations, far more than the diminutive Sessions, whom Trump mocked.

"He looks like the kind of guy who sits at the head of a table," a source familiar with the matter said of Whitaker.

Questions arise

Even as he claimed on Friday not to know Whitaker, it was clear Trump maintained an affinity for him, praising his qualifications for the job as he insisted Whitaker was being unfairly maligned.

Some legal scholars -- including George Conway , the husband of Trump counselor Kellyanne Conway -- said they thought Whitaker's appointment is unconstitutional because he is not a Senate-confirmed official. Other critics have slammed Trump's decision to appoint Whitaker as acting attorney general over Deputy Attorney General Rod Rosenstein because the move puts Whitaker in charge of special counsel Robert Mueller's probe, which Whitaker had been publicly critical of.

Trump insisted Friday that he had not spoken with Whitaker about the Mueller investigation.

"I didn't speak to Matt Whitaker about it. I don't know Matt Whitaker," Trump said.

The President's move to distance himself from Whitaker is a familiar refrain Trump has used when associates of his have become embroiled in controversy.

When federal prosecutors targeted his longtime former attorney Michael Cohen, Trump insisted Cohen handled only a "tiny, tiny fraction" of his legal work. Before that, he claimed that his indicted former campaign chairman Paul Manafort worked for him for "a very short period of time." And shortly before ousting his chief White House strategist Steve Bannon, who also helmed his campaign, Trump maintained Bannon "came on very late."

Still, the President praised Whitaker as "very highly thought of" and said that Whitaker is only taking heat because "anybody that works for me, they do a number on him."

"Matt Whitaker is a very smart man, he is a very respected man in the law enforcement community, top of the line," Trump said. "He's acting, I think he'll do a very good job and we'll see what happens."

In an email to Department of Justice staff on Friday, Whitaker vowed to lead "a fair Department with the highest ethical standards, that upholds the rule of law, and seeks justice for all Americans."

Sense of concern

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Trump's comments came as a growing sense of concern developed inside the White House over the negative reaction to Whitaker being tapped as the acting chief law enforcement official. Several senior officials said they were surprised by the criticism and believe it could potentially jeopardize his chances to remain in the post if it continues to dominate headlines.

It was not widely known among the staff that he had commented repeatedly on the special counsel's investigation in interviews and on television -- an irony given that Whitaker's TV appearances helped him land his job at the Justice Department and people close to Trump encouraged Whitaker to keep up his TV appearances to draw Trump's attention.

Whitaker was tapped by the White House to serve as Sessions' chief of staff in September 2017, with sources describing then-White House counsel Don McGahn as the person behind the hiring.

McGahn was drawn to Whitaker because he had a stalwart reputation in right-wing legal circles and because the White House wanted someone who was competent, could mind Sessions and could "keep things on the rails" at the Justice Department.

Leonard Leo, the executive vice president of the Federalist Society, said he recommended Whitaker for that post.

"I recommended him and was very supportive of him for chief of staff for very specific reasons," Leo told CNN. "Jeff Sessions needed a reliable conservative, a strong manager, and someone who had credibility who had previously served the department. Whitaker was a very good former US attorney and is a very good manager. He's a no-nonsense, get-it-done kind of guy."

Whitaker and White House chief of staff John Kelly developed a close relationship too. Kelly would often call Whitaker to convey when Trump was unhappy with something at the Justice Department or with Sessions in particular, and another source said Kelly and Whitaker were "cut from the same cloth."

Whitaker also worked to forge a relationship with the President's daughter Ivanka Trump and son-in-law Jared Kushner during trips to the White House, understanding they were key to moving up in Trump's eyes.

George Terwilliger III, a former deputy attorney general who is a Sessions ally and familiar with his senior staff, described Whitaker as a "good lawyer" with "good political skills and instincts" and said he had grown close to the White House.

Terwilliger said Whitaker's position had put him in contact with the White House "where he's held in pretty high regard."