WASHINGTON — President Trump said on Friday that he had not yet spoken to the new acting attorney general, Matthew G. Whitaker, about the special counsel investigation, and he distanced himself from Mr. Whitaker — long considered one of the president’s loyalists — by suggesting that he did not know him.
Mr. Whitaker, who now oversees the investigation, has visited the Oval Office several times and is said to have an easy chemistry with the president, according to people familiar with the relationship. And the president has regarded Mr. Whitaker as his eyes and ears at the Justice Department.
“I don’t know Matt Whitaker,” Mr. Trump told reporters as he left Washington for a weekend trip to Paris. Mr. Trump emphasized that while he did not know Mr. Whitaker, he knew his reputation well. Matt Mr. Whitaker “is a very respected man,” Mr. Trump said.
Mr. Whitaker has publicly sided with Mr. Trump in saying that the investigation into Russian election interference and any connection to the Trump campaign led by Robert S. Mueller III, the special counsel, is an overreach. That has raised questions about what changes Mr. Whitaker could make to Mr. Mueller’s mandate, particularly changes that might benefit Mr. Trump.
The United States Court of Appeals for the District of Columbia Circuit also wants to know what impact Mr. Whitaker will have on the special counsel’s investigation. On Friday, the court requested a report from both the Justice Department and the Mueller team “addressing what, if any, effect” Mr. Whitaker’s appointment has on the case, which was previously being overseen by Rod J. Rosenstein, the deputy attorney general.
Mr. Trump fired Attorney General Jeff Sessions on Wednesday after months of publicly shaming him for recusing himself from the Russia investigation. Mr. Whitaker had been serving as Mr. Sessions’s chief of staff.
In that role, Mr. Whitaker helped to stabilize the tense relationship between Mr. Trump and Mr. Sessions, according to officials who were familiar with the dynamic.
Mr. Whitaker attended meetings at the White House; in some cases, the president and the attorney general were both there, officials who were also present said.
In August, when the relationship between Mr. Trump and Mr. Sessions hit a low point and the two men exchanged a rare public tit-for-tat, Mr. Whitaker attended a meeting on prison reform with both of them later that day.
Yet, on Friday morning, Mr. Trump said four times that he did not know Mr. Whitaker.
Democrats have called for Mr. Whitaker to recuse himself from the special counsel investigation over what they see as his conflicts of interest, including his public criticism of the inquiry and his ties to a witness in the investigation. The witness, Sam Clovis, is a former Trump campaign aide and a former candidate for Iowa state treasurer. In 2014, Mr. Whitaker was the chairman of Mr. Clovis’s unsuccessful campaign.
Mr. Trump, on Friday, suggested he was a little surprised that Mr. Whitaker’s appointment would draw such criticism.
“You didn’t have any problems with Matt Whitaker when he was working for Jeff Sessions,” Mr. Trump said.
“No matter who I put in, they go after him,” Mr. Trump said of his appointees. “It’s very sad.”
Senator Chuck Schumer of New York, the minority leader, sent the president a letter on Friday requesting explanations of Mr. Trump’s justifications and authorities to name Mr. Whitaker to replace Mr. Sessions, a decision that goes against the department’s succession plan to turn first to the deputy attorney general — Mr. Rosenstein — when the top job is vacant. The president has publicly criticized Mr. Rosenstein, as well.
“Mr. Whitaker is a political appointee who is not serving in a Senate-confirmed position in the Justice Department,” Mr. Schumer wrote. “I am not aware of any precedent for appointment of an official who has not been confirmed by the Senate to serve as acting attorney general.”
Senator Richard Blumenthal, Democrat of Connecticut, said in an interview on Friday that he was considering filing a lawsuit to contest Mr. Whitaker’s appointment, most likely on grounds raised by Mr. Schumer.
“There are a number of very serious constitutional issues raised by this deeply flawed appointment,” Mr. Blumenthal said.
Mr. Trump, however, has authorities provided in a separate law that gives him options for making temporary appointments without Senate confirmation.
Speaking to reporters Friday morning, Mr. Trump bristled at criticism that Mr. Whitaker was not the right choice to run the department, because, as Mr. Schumer said, Mr. Whitaker is not currently serving in a Senate-confirmed position.
“Mueller was not Senate confirmed. So, he’s doing a report. He wasn’t Senate confirmed,” Mr. Trump said. “Whitaker was Senate confirmed. And now he doesn’t need this, but he was Senate confirmed at the highest level when he was the U.S. attorney from Iowa.”
Mr. Whitaker was confirmed by the Senate when he served as the United States attorney for the Southern District of Iowa during the George W. Bush administration. But so was Mr. Mueller. In 2001, Mr. Mueller was confirmed by the Senate to be the F.B.I. director. And he went through previous Senate confirmations to serve as the United States attorney in the Northern District of California as well as when he served as the assistant attorney general at the Justice Department in the early 1990s.
The special counsel position is not one that requires Senate confirmation.