WASHINGTON — President Trump said on Saturday that his chief of staff, John F. Kelly, would step down by the end of the year, the latest move in a long-planned staff shake-up as the president heads into the 2020 campaign facing growing peril from the special counsel and newly empowered Democrats.
The departure of Mr. Kelly, who had been brought in last year to impose order on the West Wing but found managing Mr. Trump an impossible task, had been rumored for months, and Mr. Trump announced it to reporters before departing for the Army-Navy football game in Philadelphia. He said a replacement would be named in the next day or two.
“John Kelly will be leaving — I don’t know if I can say ‘retiring,’” the president said. “But he’s a great guy. John Kelly will be leaving at the end of the year.”
Mr. Trump has settled on Nick Ayers, a youthful but experienced political operative who serves as chief of staff to Vice President Mike Pence, as his top choice to replace Mr. Kelly, people familiar with the matter said. In Mr. Ayers, Mr. Trump sees what Mr. Kelly, a career military officer, was not: a wily political operative whose focus would be on politics and campaigning as the president looks toward his re-election bid.
But Mr. Ayers, 36, who has young children and wants to return home to Georgia with his family, has so far agreed to serve only on an interim basis through the spring. Mr. Trump, who does not want more turnover, is pressing Mr. Ayers to agree to a more permanent stay, those familiar with the discussions said.
If the president ultimately turns to another candidate, potential choices include the Treasury secretary, Steven Mnuchin; his budget director, Mick Mulvaney; and the United States trade representative, Robert Lighthizer.
The announcement of Mr. Kelly’s departure comes as the White House braces for the final stages of the investigation by the special counsel, Robert S. Mueller III, including a report detailing his findings on questions of collusion and obstruction of justice. The president also faces a string of oversight investigations into his administration from Democrats after they take control of the House next month.
As he confronts this reality, Mr. Trump is finally carrying out the staff shake-up that he had been considering for months. On Friday, he announced his pick for attorney general, William P. Barr, an advocate of strong presidential powers, and told reporters he had settled on Heather Nauert, a former “Fox & Friends” host and most recently the State Department spokeswoman, as his nominee for United Nations ambassador.
While Mr. Trump is eager for Mr. Ayers to join that list, it is unclear whether the aide, who lacks experience in government beyond his stint with Mr. Pence, is what the president needs in the top West Wing post as he heads into what allies expect will be the most tumultuous year yet of his presidency. Some former administration officials said they feared that Mr. Ayers would feed Mr. Trump’s predisposition to focus more on politics, imperiling any chance of advancing bipartisan legislation.
But other advisers said the move would be helpful to the president, exactly because Mr. Ayers would play to his instincts. “Every president at natural inflection points makes significant changes in their administration,” said Corey Lewandowski, an informal adviser to Mr. Trump. “The president relied on information and people he didn’t know to staff the administration. Now, he’s gone back to people he knows. They’re on his team, and that’s what is needed.”
But Mr. Ayers is already a divisive figure in the Trump orbit. When it became clear that Mr. Trump, who has an unusual affinity for Mr. Ayers, was leaning toward him to replace Mr. Kelly, several top aides told the president that they took issue with it and that it could lead to a staff exodus.
If Mr. Ayers accepts the job, his appointment would be seen inside the White House as a coup for Ivanka Trump, the president’s daughter, and her husband, Jared Kushner, who clashed with Mr. Kelly and are seen as close to Mr. Ayers. The view inside is that they are now “running the building,” one of the president’s allies said.
Mr. Kelly had long complained that Ms. Trump and Mr. Kushner, both top advisers to the president, were “playing government.” He had repeatedly tried to limit their influence amid complaints from others in the West Wing that they did not operate within the system.
When Mr. Kelly, a retired four-star Marine general, entered the White House in July 2017 with the goal of instilling order in a disorderly West Wing, he lent a patina of respectability to a White House that at the time was staffed almost entirely by people who had never before served in government.
Despite his imposing military credentials, however, Mr. Kelly slowly realized the futility of trying to control the president, and ultimately resigned himself to a stalemate of coexistence, simply letting Trump be Trump and complaining to his colleagues about how miserable he was in the job. In the past year, he has often come to work late and left early, telling colleagues, “I’m leaving and I’m not coming back.”
His overt dissatisfaction meant that no one in the White House ever expected him to stand by a statement he issued earlier this year to quell the constant rumors of his impending departure. While he said at the time that he would remain in the job through the re-election campaign in 2020, Mr. Trump himself told allies that he expected Mr. Kelly to be around only through the midterm elections.
Mr. Kelly, who did not show up for work on Friday, met with Mr. Trump that evening in the White House residence, just before a senior staff dinner, to hash out the details of his departure, according to people familiar with the meeting. Mr. Pence and Mr. Ayers also attended.
In the residence on Friday night, the president and Mr. Kelly agreed that the departing chief would break his own news on Monday, announcing his exit to senior White House staff members. But Mr. Trump ultimately broke the news himself on Saturday afternoon.
Mr. Kelly’s departure is expected to have a ripple effect across the upper echelons of the West Wing staff, as well as in Mr. Trump’s cabinet. One of the biggest question marks is the fate of Kirstjen M. Nielsen, the secretary of homeland security. Ms. Nielsen has clashed repeatedly with Mr. Trump, and at times relied on Mr. Kelly, who was previously her boss at the agency, to defend her.
For weeks, Mr. Trump has been offering her position to other people. At one point, Mr. Trump even broached the possibility that Thomas P. Bossert, a former homeland security adviser, would return and run the agency. But Mr. Bossert, who was forced out of the administration after John R. Bolton became national security adviser, made it clear he would not accept the position.
The ceaseless West Wing backbiting that captures headlines has belied the reality of working there, which is that aides form tight cliques and burrow into those friendships to endure the chaos of the work environment.
Other protégés of Mr. Kelly like Zachary D. Fuentes, the deputy chief of staff, are also seen as particularly vulnerable without Mr. Kelly in the top job. Mr. Fuentes, who has earned ridiculing nicknames, including “Zotus” (a play on Potus, short for president of the United States) and “prime minister,” for his large ego, has already approached other departments in the administration for a position, but has cultivated few allies. Mr. Trump continues to blame him and Mr. Kelly for letting him miss a World War I battlefield commemoration outside Paris because of bad weather.
The White House communications office, which Mr. Trump has complained about for two years, is also set to undergo a restructuring. The overlap in officials has bred chronic confusion. But those who are expected to stay include Bill Shine, the newly hired communications director, who has tried to foster a relationship with Ms. Trump by helping her with her news media strategy.
On Saturday, Mr. Kelly did not attend the Army-Navy game with the president, who stood on the field for the singing of the national anthem with Jim Mattis, the defense secretary, by his side. Watching the first half of the game from the Army stands, the president was then joined by Gen. Mark A. Milley, whom he had announced on Twitter on Saturday morning as his nominee to serve as chairman of the Joint Chiefs of Staff.
Julie Hirschfeld Davis, Katie Rogers and Eileen Sullivan contributed reporting.