WASHINGTON — The White House counsel, Donald F. McGahn II, will leave the administration this fall, President Trump tweeted Wednesday morning, leaving the president’s side just as the sprawling investigation into Russian election interference reaches a crescendo.
In addition to stripping the White House of another top official, Mr. McGahn’s departure may fuel concerns about how the president has interacted with witnesses and potential witnesses in the Russia inquiry. Mr. McGahn is a key witness to whether the president tried to obstruct the investigation, and has cooperated extensively in the investigation.
The departure of the top lawyer in the White House has been rumored for months. In his tweet, Mr. Trump said that Mr. McGahn would leave after the Senate votes on the confirmation of Judge Brett Kavanaugh to fill the vacant seat on the Supreme Court later this fall, the culmination of a quiet but intensive effort he directed to remake the federal courts by installing scores of conservative judges.
“I have worked with Don for a long time and truly appreciate his service!” Mr. Trump said in the Twitter post.
But the relationship between the president and Mr. McGahn has been rocky since he failed to stop the attorney general, Jeff Sessions, from recusing himself a year ago from the Justice Department investigation into Russian interference in the 2016 campaign. At the time, Mr. Trump exploded at Mr. McGahn and said he needed an attorney general who would protect him.
The president also asked Mr. McGahn last June 2017 to fire the special counsel, Robert S. Mueller III. Mr. Trump ultimately backed down after Mr. McGahn threatened to resign rather than carry out the president’s directive.
Mr. McGahn, who was the top lawyer for the Trump campaign, has considered resigning as counsel repeatedly, according to people who have spoken with him. He stayed on at the urging of Senator Mitch McConnell, the majority leader from Kentucky, and to execute a strategy he spearheaded to appoint conservative judges to the federal bench. Mr. McGahn is also loyal to Mr. Trump’s chief of staff, John F. Kelly.
Mr. McGahn’s departure after the midterm congressional elections was widely expected, and Mr. McGahn had laid the groundwork for his own resignation, persuading Mr. Trump to hire Emmet T. Flood — who represented Bill Clinton in impeachment proceedings — as his lead White House lawyer dealing with the special counsel inquiry, in order to position Mr. Flood to succeed him in the counsel post, according to people close to the discussions.
Still, some Republicans reacted to the news with alarm. Senator Charles E. Grassley of Iowa, the chairman of the Senate Judiciary Committee, said he was concerned about Mr. McGahn’s impending departure, pleading with Mr. Trump on Twitter not to let him leave the White House.
But some members of conservative legal circles in which Mr. McGahn has worked suggested that he had grown weary of serving as the top lawyer in a White House that has drawn more than the usual share of legal scrutiny.
George T. Conway III, who withdrew last year as Mr. Trump’s choice for a top post in the Justice Department, and is the husband of Kellyanne Conway, the counselor to the president, responded to Mr. Grassley by tweeting, “remember the eighth amendment, senator.” It was a reference to the prohibition in the Constitution against cruel and unusual punishment.
Mr. McGahn was interviewed several times by Mr. Mueller’s investigators, disclosing to them several details about episodes like the abrupt firing last May of James B. Comey, the F.B.I. director.
[The White House counsel, Donald F. McGahn II, has cooperated extensively in the Mueller inquiry.]
The firings of top Trump administration officials have brought the Russia investigation closer to the president in a variety of ways.
The firing of Mr. Comey prompted the appointment of Mr. Mueller. The president’s first national security adviser, Michael T. Flynn, was fired in the first weeks of the administration, which led to Mr. Flynn’s cooperation with the special counsel investigation. And the departure of Mr. Trump’s chief strategist, Stephen K. Bannon, left a rift between the two men just as Mr. Bannon met with Mr. Mueller.
Mr. Trump said recently that he was willing to speak with Mr. Mueller. But in June 2017, the president told Mr. McGahn that the special counsel had to be fired because he had several conflicts of interest, including a dispute years ago over membership fees at Mr. Trump’s golf club in Sterling, Va. Mr. Trump also said that Mr. Mueller should be disqualified from leading the investigation because he had been interviewed to be the interim F.B.I. director on the day before he was appointed special counsel.
The White House has long denied that the president ever considered firing Mr. Mueller.
But he has recently been openly attacking the special counsel in an abrupt shift in tone. Mr. Trump had for the most part heeded the advice of his lawyers not to target Mr. Mueller’s team directly.