WASHINGTON — When President Trump learned that the Justice Department was dropping a case against a former F.B.I. official whom he considered one of his longtime enemies, his immediate response was anger. As he flipped on the television Friday and watched how the story was being covered, that anger only mounted.
Since taking office, Mr. Trump has searched for an attorney general who would function much as Roy Cohn did for him as his personal lawyer and fixer in the 1970s — a warrior committed to protecting him and going after his foes. The president thought he had found that person in William P. Barr. But now, people close to Mr. Trump say, he is not so sure.
The president was cheered this week when Mr. Barr moved to reduce the sentence of a convicted presidential friend, only to be shocked when the attorney general publicly called on Mr. Trump to stop tweeting about it. And after his livid reaction to the Justice Department’s decision to drop a separate case, which he heard about without any advance notice, he learned that Mr. Barr was intervening more favorably on behalf of another presidential ally.
The whipsaw events of recent days have bewildered much of Washington, including some of the people around the president and his attorney general. Once seen as a lock step partnership, it now may be the most complicated relationship in town. The six blocks between the White House and the Robert F. Kennedy Department of Justice Building have become a political buffer zone and no one can be entirely sure what comes next.
Critics assume it is all a Kabuki dance, cynical theater meant to preserve Mr. Barr’s credibility as he executes Mr. Trump’s personal political agenda while pretending to look independent. And it is certainly true that, even now, Mr. Barr continues to demonstrate a willingness to personally take charge of cases with Mr. Trump’s interests at stake.
But insiders insist the tension is real, with potentially profound consequences for an administration that has redrawn the lines at the intersection of politics and law enforcement. Barely a week after being acquitted in a Senate impeachment trial, Mr. Trump is demanding that some of the people whose actions he believes led to his troubles be charged, convicted and sent to prison, and it is not clear that even Mr. Barr is willing or able to go as far as the president wants.
In his only comment on the matter on Friday, Mr. Trump pushed back against Mr. Barr a day after the attorney general told ABC News that the president was making it “impossible for me to do my job” by tweeting about criminal cases and declared that he was “not going to be bullied.”
Mr. Trump cited another comment Mr. Barr made in the same interview affirming that the president had never actually asked for any specific actions in a criminal case. “This doesn’t mean that I do not have, as President, the legal right to do so, I do, but I have so far chosen not to!” Mr. Trump added. The “so far” in there, of course, hung online as a kind of sword of Damocles waiting to fall.
Only in the hours after that tweet did the news emerge that Mr. Barr’s department was dropping a case against Andrew G. McCabe, the former deputy F.B.I. director blamed by Mr. Trump for his role in the investigation into Russian election interference. Two people close to the matter said the Justice Department did not give the president a heads up about the decision.
Then came the more welcome news for the Oval Office that Mr. Barr had ordered a re-examination of the case of Michael T. Flynn, the president’s former national security adviser who pleaded guilty to lying to the F.B.I. about his contacts with Russia. The new review raised the question of whether Mr. Flynn will actually go to prison.
Mr. Trump has bitterly decried “what Flynn has gone through” while believing that Mr. McCabe has unfairly walked, people close to him said. The president on Friday was angrier about the decision not to prosecute Mr. McCabe than he was at Mr. Barr’s comments in his interview, the people said.
Mr. Trump made no mention of any of those newer developments on Twitter or in several encounters with reporters before flying to Florida for the weekend. But he sometimes waits to publicly respond to such news until after an evening watching Fox News or hearing from friends.
On the fifth floor of the Justice Department, Mr. Barr’s team braced for what they feared would be a stream of critiques and humiliations from the president in what one predicted could be a death by a thousand cuts, not unlike what happened to the last attorney general, Jeff Sessions, who was tormented by the president after recusing himself from the Russia investigation.
Mr. Sessions, like other cabinet members, stoically absorbed Mr. Trump’s invectives, rarely standing up for himself or his employees, even as the president paralyzed, undercut and neutered him. Like other original cabinet members, he left the administration publicly humiliated and vastly diminished.
Mr. Barr faced many risks in speaking out on ABC, according to people close to him. But he knew that no amount of public fealty would stave off a public drubbing or even an abrupt dismissal.
For now, though, there is no expectation at the Justice Department or the White House of an escalation to that level. While Lou Dobbs on Fox Business Network excoriated Mr. Barr for rebuking the president, other Fox hosts who have Mr. Trump’s ear, like Sean Hannity and Laura Ingraham, were generally supportive of the attorney general. Tucker Carlson, another trusted television personality, treated Mr. Barr’s ABC interview like a nonevent on his Fox News show Thursday night.
Ms. Ingraham, who is close to Mr. Barr, said the attorney general was not breaking with the president but, in effect, reassuring him that the Justice Department’s leadership would carry out Mr. Trump’s wishes to clean up what they see as the corruption of his predecessor and that the tweets were neither necessary nor helpful.
“Barr was basically telling Trump, ‘Don’t worry, I got this,’” Ms. Ingraham said on her show.
Some of the attorney general’s critics saw it the same way. Nine Democratic senators, including two presidential candidates, Bernie Sanders of Vermont and Elizabeth Warren of Massachusetts, sent a letter to Mr. Barr on Friday calling on him to resign.
His protestations of independence were not credible, they wrote, given his department’s behavior. “It demonstrates that you lied to Congress during your confirmation hearing when you stated that you would ‘keep the enforcement process sacrosanct from political influence,’ and it reveals your unwillingness or inability to maintain the integrity of the D.O.J. and to uphold justice and the rule of law,” the senators wrote.
Ms. Warren and three other Democratic senators also unveiled legislation barring an attorney general and other top Justice Department officials appointed by a president from participating in matters related to the president, his family or his campaign associates.
Although Mr. Trump and Mr. Barr both said the president has not directly asked for any specific inquiries, the president has long pressured law enforcement officials both publicly and privately to open investigations into political rivals and to drop inquiries into him or his associates.
Since Watergate, past presidents in both parties have had a tradition in place aimed at preventing political influence from the White House on Justice Department investigations, especially criminal inquiries that involved administration officials or friends of the president.
“It tries to prevent the interference by forcing all White House contact to go through a funnel at the top of the Justice Department,” said John Yoo, a law professor at the University of California, Berkeley who served in the Justice Department under President George W. Bush.
Mr. Trump’s first White House counsel, Donald F. McGahn II, issued similar rules in a Jan. 27, 2017, memo that prohibited White House officials from communicating with most Justice Department officials about “ongoing or contemplated cases.” Only the president, vice president or White House counsel was allowed to initiate such communications, Mr. McGahn wrote, and they must be directed to the attorney general or three other top Justice Department officials.
“In order to ensure that D.O.J. exercises its investigatory and prosecutorial functions free from the fact or appearance of improper political influence, these rules must be strictly followed,” Mr. McGahn wrote.
But scholars said Mr. Trump is right that he has the power to intervene if he chooses. Under Article II of the Constitution, any president has the authority to directly oversee criminal cases carried out by the Justice Department. There are no statutes that limit the contact between the White House and the Justice Department.
“The president can do what he wants,” said Bruce Green, a law professor at Fordham University. “His only restraints are self imposed. There are no legislative restraints.”
The only real recourse, he added, would be impeachment. “If a president attempted to misuse the Justice Department and its criminal justice power for private ends, that’s an abuse of power that is potentially impeachable,” Mr. Green said. “We can guess in 2020 how that would play out.”
Maggie Haberman contributed reporting from New York, and Katie Benner and Michael Crowley from Washington.