Before his White House visit, Mr. Trump is expected to head to friendlier territory: a gathering of Republican lawmakers on Capitol Hill. He will be joined by Elon Musk, the billionaire supporter tasked by Mr. Trump on Tuesday to lead an effort to make government smaller and more efficient. Mr. Musk, who has ascended to a position of wide-ranging influence in Mr. Trump’s transition, was traveling with the president-elect to Washington, a person close to Mr. Trump said.

The last meeting between Mr. Trump and Mr. Biden was anything but cordial: At a debate in Atlanta in June, Mr. Biden told Mr. Trump that he was a “convicted felon” with “the morals of an alley cat.” Mr. Trump called Mr. Biden a “Manchurian candidate” who “gets paid by China.” After a confusing answer by Mr. Biden, Mr. Trump said he did not understand, adding, “I don’t think he knows what he said, either.”

There is little evidence that the ill will between the two men has eased in the week since Mr. Trump soundly defeated Vice President Kamala Harris to reclaim the presidency, dealing a serious blow to Mr. Biden’s agenda and legacy after half a century in public life.

What the rivals will say to each other behind closed doors is unclear, and so is what they might say publicly. They are scheduled to have a brief photo op in front of reporters after the meeting ends.

But history suggests that Mr. Biden and Mr. Trump may treat each other with the courtesy that eluded them during much of the past four years, and certainly during the campaign.

In 2016, after Mr. Trump defeated Hillary Clinton, President Barack Obama invited him to the Oval Office. Their closed-door meeting that was supposed to last under a half-hour went on for nearly 90 minutes. After it was over, Mr. Trump thanked Mr. Obama and said he looked forward to receiving his counsel and advice during his presidency.

That did not happen, and the friendly tone that Mr. Trump exhibited toward Mr. Obama that day was rarely heard again by Democrats during his four years in office. After Mr. Biden defeated him in 2020, Mr. Trump refused to concede the election and never invited Mr. Biden for the traditional meeting in the White House.

It is unlikely that Mr. Biden has forgotten that snub (though it is not clear that he wanted to meet with Mr. Trump in 2020). But Mr. Biden is an institutionalist who has long expressed respect for the trappings and traditions of the White House and the Senate, where he served for 36 years before becoming Mr. Obama’s vice president. That is most likely what motivated him to offer Mr. Trump the invitation that he did not receive himself.

Here’s what else to know:

Melania Trump: The former first lady will not attend the White House visit with her husband, according to a person briefed on the plans. Jill Biden, the current first lady, had invited her, in keeping with tradition for presidential spouses. But Mrs. Trump, who often eschewed the spotlight during Mr. Trump’s first term, declined.

Government overhaul: Mr. Trump said on Tuesday that Elon Musk and Vivek Ramaswamy, two of his most prominent wealthy backers, would lead an effort to restructure and even dismantle parts of the federal government. They will run what Mr. Trump called the Department of Government Efficiency, driving “drastic change” with major cuts and new efficiencies in bloated agencies. But Mr. Trump’s announcement left a lot unanswered.

Defense secretary: Mr. Trump veered away from a traditional choice for defense secretary, saying he would nominate Pete Hegseth, a Fox News host and veteran of the Iraq and Afghanistan wars, to the position.

Intelligence chief: Mr. Trump said that his nominee to lead the C.I.A. would be John Ratcliffe, a former Texas congressman who served as the director of national intelligence during Mr. Trump’s first term. If confirmed by the Senate, Mr. Ratcliffe would most likely become the most influential voice on intelligence matters in the next administration.

Senate leadership: Republican senators will vote via secret ballot on Wednesday to choose their leader. Senators John Thune of South Dakota and John Cornyn of Texas are seen as having an edge over Senator Rick Scott of Florida, who is seen as the favorite of the party’s right flank.

Special counsel to step down: Jack Smith, who pursued two federal prosecutions of Donald J. Trump, plans to finish his work and resign before Mr. Trump takes office, people familiar with his plans said. Mr. Smith’s goal, they said, is to not leave any significant part of his work for others to complete and to get ahead of the president-elect’s promise to fire him within “two seconds” of being sworn in.

House update: Control of the House of Representatives remains unclear, though analysts say Republicans are favored to win a narrow majority when all of the votes are counted in close races around the country. Six of the 12 uncalled races that will determine the balance of power are in California, where the counting of ballots typically takes longer than in any other state.

More Trump picks: Mr. Trump announced on Tuesday that he had chosen Representative Michael Waltz of Florida to be his national security adviser, turning to a former Green Beret who has taken a tough line on China. He also said that he intended to nominate Mike Huckabee — the former governor of Arkansas and the father of the state’s current governor, Sarah Huckabee Sanders, a former Trump press secretary — to be the U.S. ambassador to Israel.

Maggie Haberman contributed reporting.

Mr. Smith, who since taking office two years ago has operated under the principle that not even a powerful ex-president is above the law, now finds himself on the defensive as he rushes to wind down a pair of complex investigations slowed by the courts and ultimately made moot by Mr. Trump’s electoral victory.

Mr. Smith’s office is still drawing up its plan for how to end the cases, and it is possible that unforeseen circumstances — such as judicial rulings or decisions by other government officials — could alter his intended timeline. But Mr. Smith is trying to finish his work and leave before Mr. Trump returns to power, the people familiar with his plans said.

The election’s outcome spelled the end of the federal cases against Mr. Trump, since Justice Department policy has long held that a sitting president cannot be prosecuted for crimes. A Supreme Court ruling this summer significantly expanded the scope of official presidential conduct that cannot be prosecuted even after leaving office.

As he prepares for his last act as special counsel, Mr. Smith’s ultimate audience will not be a jury, but the public.

Department regulations call for him to file a report summarizing his investigation and decisions — a document that may stand as the final accounting from a prosecutor who filed extensive charges against a former president but never got his cases to trial.

It is not clear how quickly he can finish this work, leaving uncertain whether it could be made public before the Biden administration leaves office. But several officials said he has no intention of lingering any longer than he has to, and has told career prosecutors and F.B.I. agents on his team who are not directly involved in that process that they can start planning their departures over the next few weeks, people close to the situation said.

The people spoke on condition of anonymity because they were not authorized to discuss personnel moves.

Mr. Smith, a former war crimes prosecutor, is now a target of pro-Trump Republicans who portray him as the embodiment of a Democratic effort to use “lawfare,” the so-called weaponization of the Justice Department, to destroy Mr. Trump.

On Friday, Republican lawmakers told Justice Department officials who had worked on the Trump cases to preserve all of their communications for investigators. That is a sure sign that a new balance of power in Washington will make Mr. Smith among those being hunted by congressional investigators and others.

That same day, Mr. Smith’s team filed a court document taking the first step to wind down his two-pronged prosecution of Mr. Trump. The prosecutor asked for and received a monthlong pause to the filing deadlines in his case in Washington charging Mr. Trump with conspiring to overturn the 2020 election.

Mr. Smith said he needed until Dec. 2 to decide exactly how to wind down that case and his other Trump prosecution, in which Mr. Trump has been charged with mishandling classified national security documents after leaving office and obstructing efforts to retrieve them. The documents case was dismissed by Judge Aileen Cannon of the Federal District Court in Fort Pierce, Fla. That decision is currently being appealed in federal court in Atlanta.

Referring to the fact that the defendant would soon take office again as president, Mr. Smith said in Friday’s filing that he needed a month “to assess this unprecedented circumstance and determine the appropriate course going forward consistent with Department of Justice policy.”

The type of special counsel report being prepared by Mr. Smith and his team is technically supposed to be directed to the attorney general.

Attorney General Merrick B. Garland has repeatedly signaled he intends to release such reports to the public, although with some redactions to comply with broader department rules.

In some cases, the findings contained in special counsel reports can be revelatory. In February, the special counsel Robert K. Hur’s report concluded that criminal charges were not warranted for President Biden for retaining classified documents from his time as vice president, but offered a unflattering assessment of Mr. Biden’s memory and cognitive capacity.

Justice Department regulations require a special counsel’s report to explain why the prosecutor decided to file the charges they did, and why they decided not to file any other charges they considered.

But like much of Mr. Smith’s work involving Mr. Trump, this step is fraught with both technical and practical challenges that could make the report significantly different — and shorter — from the lengthy tomes produced by other recent special counsels. It also unlikely to contain much in the way of new or revelatory disclosures.

Mr. Smith, who has been the subject of round-the-clock protection after receiving death threats since taking over, has already described much of the evidence and legal theories behind the election obstruction indictment. Since he filed two separate and lengthy indictments last year against Mr. Trump, he has supplemented that record with scores of court filings elaborating on the allegations.

One potential wrinkle for the filing and release of Mr. Smith’s report is that it may have to undergo a careful review by U.S. intelligence agencies for any classified information. That can be a lengthy process. Intelligence agencies took weeks to review Mr. Hur’s report.

But in the case of Mr. Smith’s final report, most of that vetting has already been done, so officials expect that step to take little time.

The big question now, assuming Mr. Smith finishes the report on his current schedule, is whether Mr. Garland will release the findings before he leaves office, or defer the release to the Trump team, which might not make its contents public.

A spokeswoman for Mr. Garland declined to comment.

Mr. Trump said on Tuesday that Elon Musk and Vivek Ramaswamy will lead what he called the Department of Government Efficiency. It will be, he said, “the Manhattan Project” of this era, driving “drastic change” throughout the government with major cuts and new efficiencies in bloated agencies in the federal bureaucracy by July 4, 2026.

“A smaller Government, with more efficiency and less bureaucracy, will be the perfect gift to America on the 250th Anniversary of The Declaration of Independence,” Mr. Trump wrote in a statement. “I am confident they will succeed!”

The statement left unanswered all kinds of major questions about an initiative that is uncertain in seriousness but potentially vast in scope. For starters, the president-elect did not address the fact that no such department exists. And he did not elaborate on whether his two rich supporters would hire a staff for the new department, which he said is aimed in part at reducing the federal work force.

Mr. Musk, who became one of Mr. Trump’s biggest campaign contributors, said before the election that he would help the president-elect cut $2 trillion from the federal budget. But he did not explain in any detail how that would be accomplished or what parts of the government would be slashed.

“This will send shockwaves through the system, and anyone involved in Government waste, which is a lot of people!” Mr. Musk said in the statement.

The statement by Mr. Trump also did not address how Mr. Musk in particular would handle this task, without creating conflicts of interest, given that SpaceX has secured more than $10 billion worth of federal contracts over the last decade.

SpaceX, Tesla and other companies Mr. Musk created, such as Neuralink, which is manufacturing computer chips that are implanted in the brain, have also been targeted recently in at least 20 different investigations or lawsuits by federal agencies. That means Mr. Musk will somehow be watching over agencies that police his companies.

Mr. Trump’s statement said only that this new department would “provide advice and guidance from outside of government,” suggesting that Mr. Musk will not take a formal role as a federal official.

Slashing government regulations and spending became a top priority for Mr. Musk as his frustrations have grown, particularly this year, with what he considers excessive or redundant oversight by the Federal Aviation Administration and the Interior Department, as SpaceX sought launch licenses to continue testing its newest rocket called Starship.

SpaceX’s Texas launch site is set up next to a national wildlife refuge and state park, requiring detailed environmental reviews before launches, a process that has infuriated Mr. Musk, slowing his plans to take humans to Mars.

The name of the new department — DOGE — appeared to be a play on another one of Mr. Musk’s many investments: the cryptocurrency Dogecoin, which the billionaire regularly promotes to others.

Mr. Ramaswamy, a 39-year-old political novice, challenged Mr. Trump for the Republican nomination before dropping out and becoming a fervent Trump acolyte. As Mr. Trump campaigned in the last year, Mr. Ramaswamy became a frequent surrogate, singing his praises and spreading the conspiracy theories that Mr. Trump had long embraced.

As part of his message, Mr. Ramaswamy vowed to help take Mr. Trump’s promise to cut government even further. He proposed immediately eliminating the Education Department, the F.B.I. and the Internal Revenue Service by executive order. He said the federal work force should be cut by 75 percent in a mass layoff. And he said he would slash foreign aid to places like Ukraine, Israel and Taiwan.

Promises of government reform are hardly new in Washington. Previous presidents have pledged much the same, though often without quite as much flourish.

In 1993, after President Bill Clinton promised to “reinvent government,” Vice President Al Gore led the newly created National Partnership for Reinventing Government. The goal was similar to Mr. Trump’s effort — to reduce federal spending by eliminating wasteful programs, cutting unnecessary jobs and making the bureaucracy work better.

By the time it ended five years later, Mr. Gore’s effort had succeeded in reducing some overlap in government programs and cutting some federal jobs. But it fell far short of a total reinvention of the government. With about three million employees, the federal government head count has grown slightly in recent years but remains well below the peak it reached in the late 1980s.

Mr. Trump, whose political appeal was built in part on a promise to “drain the swamp” in Washington, has long taken aim at the size of the bureaucracy. But in his first term, he did little to act on those promises.

Now, he is promising that Mr. Musk and Mr. Ramaswamy will succeed where he did not.

“I look forward to Elon and Vivek making changes to the Federal Bureaucracy with an eye on efficiency and, at the same time, making life better for all Americans,” Mr. Trump wrote. “Importantly, we will drive out the massive waste and fraud which exists throughout our annual $6.5 Trillion Dollars of Government Spending.”

The result is that Mr. Trump may end up with a foreign policy team composed of deep loyalists, but with roots in familiar Republican approaches. The shift that the two men have made reflects the broader marginalization of neocons throughout the Republican Party after the disaster in Iraq and the rise of America First.

Mr. Trump’s loyalists, and much of the party, have now made a full conversion to that worldview, few more enthusiastically than Pete Hegseth, the Fox News host who was chosen as defense secretary on Tuesday.

Mr. Hegseth channels both Mr. Trump’s avowed isolationism and his impulsive interventionism. He has also backed Mr. Trump’s occasional use of force, notably the order to killing a senior Iranian general in January 2020.

Mr. Hegseth, a veteran of Iraq and Afghanistan, described his own conversion to America First to The New York Times four years ago.

“I think a lot of us who were very hawkish and believe in American military might and strength were very resistant to how candidate Trump characterized the wars,” Mr. Hegseth said. “But if we are honest with ourselves, there is no doubt that we need to radically reorient how we do it. How much money have we invested, how many lives have we invested and has it actually made us safer? Is it still worth it?”

For Mr. Rubio and Mr. Waltz, the drift from their previous positions to their current ones has been slow, evident in shadings of what they said at conservative conferences or in interviews on Fox News, and in how they altered their votes at key moments in the past few years. Ukraine has been a litmus test.

When Russia first invaded Ukraine in February 2022, Mr. Rubio, the No. 2 on the Senate Intelligence Committee, applauded the rush to send arms, aid and intelligence to the Ukrainians. So did Mr. Waltz, a former Green Beret, who enthusiastically supported giving President Volodymyr Zelensky everything he needed to drive out Russian troops.

But by this spring, each for their own reasons, Mr. Rubio and Mr. Waltz voted against the last major aid package to support Ukraine. And to justify their new position, Mr. Rubio declared that the United States could not afford to fight for Ukraine’s freedom while illegal immigrants were coming over the southern U.S. border.

For his part, Mr. Waltz wrote in an opinion essay for Fox News that President Biden “has neither explained the American objective in Ukraine nor his strategy to achieve it. Will American military spending continue until Ukraine has pushed Russia back to its prewar boundaries? Its pre-2014 boundaries? Or until the Putin regime collapses?”

In fact, Mr. Biden’s objectives have shifted. His often-repeated statement that the United States will stand by Ukraine “for as long as it takes” has morphed into “as long as we can.”

But his aides largely describe their goal as a simple one: to help put the Ukrainians in a position that they could one day enter negotiations with Russia, preferably with the upper hand on the battlefield. It seems unlikely that day will come in the 10 weeks remaining in Mr. Biden’s presidency. So almost immediately, defining objectives will fall to Mr. Waltz and, if he is nominated and confirmed, Mr. Rubio.

It may be a challenge, since their boss has insisted only that there should be a deal — the details of which he has never described. Presumably, it would give Russia a large chunk of the country in return for peace and a declaration that Ukraine would not enter the North Atlantic Treaty Organization for years or decades to come.

“They are still internationalists,” said Richard Haass, a longtime Republican national security official and diplomat, who worked for President George H.W. Bush in the aftermath of the fall of the Berlin Wall and President George W. Bush in the run-up to the war in Iraq. “But the test of what kind of internationalist will come in how far they are willing to distance themselves from Ukraine. And it will come again in what kind of tools they would use to confront China.”

Nearly 10 years ago, when Mr. Rubio was running for the Republican nomination for president against Mr. Trump, the Florida senator spoke at the Council on Foreign Relations — the heart of the traditional foreign policy establishment. He quoted John F. Kennedy and made the case that the younger Mr. Bush had made: that American power must be “motivated by a desire to expand freedom, rather than simply expand its own territory.”

“While America did not intend to become the world’s indispensable power, that is exactly what our economic and political freedoms have made us,” he told the crowd, castigating President Barack Obama and the Democratic nominee, Hillary Clinton, for being too timid in facing up to dictators from Syria to China. “The free nations of the world still look to America to champion our shared ideals.”

Today Mr. Rubio makes a different, more pragmatic and more Trumpian case: that the way to keep America out of wars is to build up its strength, invest in key technologies and domestic supply chains for critical materials, and use tariffs to block threatening imports.

Mr. Waltz is less known in the foreign policy world, though he is familiar as a commentator to viewers of Fox News, including Mr. Trump. He received four Bronze Stars after multiple combat tours in Afghanistan and Africa, and worked as a junior adviser to defense secretaries Donald H. Rumsfeld and Robert M. Gates, both of whom served in the administration of George W. Bush. Mr. Waltz also advised Vice President Dick Cheney on counterterrorism. Once, that pedigree granted a young foreign policy professional entry into the neocon inner circle.

But during his time in Congress, Mr. Waltz has espoused a national security doctrine that has increasingly jelled with Mr. Trump’s. A member of the House committees on the armed services, intelligence and foreign affairs, he has chastised NATO allies for not meeting their defense military spending commitments.

He was a vociferous critic of Mr. Biden’s withdrawal of troops from Afghanistan. “What no one can ever do for me, including this administration right now, is articulate a counterterrorism plan that’s realistic without us there,” Mr. Waltz said in an interview in the days after the withdrawal.

Of course, Mr. Trump had proposed a similar withdrawal just months before. Mr. Waltz had opposed that as well, introducing legislation to prevent a significant troop drawdown from Afghanistan unless the director of national intelligence could certify that the Taliban would not associate with Al Qaeda.

In 2023, Mr. Waltz led legislation that would authorize the president to use military force against Mexican drug cartels because of fentanyl trafficking, production and distribution. The bill echoed the war powers Congress gave Mr. Bush before the invasions of Afghanistan and Iraq.

Both Mr. Rubio and Mr. Waltz are supporters of a more hard-line economic approach toward China, as well. Although Mr. Trump’s pending picks for Treasury secretary, commerce secretary and trade representative will take a larger part in shaping tariff and trade policy, Mr. Rubio and Mr. Waltz could play an influential role. Both have supported removing permanent normal trading relations with China — a move that would result in higher tariffs on products from the country — as well as barring U.S. investment from flowing to certain Chinese companies.

Mr. Rubio has also favored sweeping economic sanctions to penalize Beijing for human rights violations. He was the co-sponsor of a 2021 law that banned the importation of any products into the United States that were made with any materials or labor from Xinjiang, a far-western province where China has carried out a crackdown against Muslim minorities.

But those bills now read as if they come from a different era, before China’s economic downturn created new vulnerabilities, and before its uneasy partnership with Russia posed a very different, more complex threat to the West.

These are issues that did not confront the first Trump administration. And the solutions are also complex. Are they addressed with Mr. Trump’s tariffs, which the president-elect describes as a cure-all, but could cost American consumers billions and fuel inflation? With more restrictions on shipping high-end semiconductors and equipments to China — a step Mr. Biden has pioneered? Or with pouring more military resources into the Pacific region, which Democrats and Republicans have promised, but don’t have the naval resources to make happen on the scale they have imagined?

Outside experts say Mr. Trump learned something from the chaos of the first term and has adjusted accordingly. “Over the past eight years, he has collected enough acolytes to staff his foreign policy and national security team with like-minded officials,” Daniel W. Drezner, a professor of international politics at the Fletcher School of Law and Diplomacy, wrote this week in Foreign Affairs.

“He is far less likely to meet resistance from his own political appointees. Other checks on Trump’s policy will also be far weaker,” he said, and the result will be that “the United States will speak with one voice on foreign policy, and that voice will be Trump’s.”

Ana Swanson contributed reporting.

In a statement announcing his pick, Mr. Trump praised Mr. Hegseth’s combat experience and support of the military and veterans. “Pete is tough, smart and a true believer in America First,” Mr. Trump said. “With Pete at the helm, America’s enemies are on notice — our military will be great again, and America will never back down.”

Mr. Hegseth is a co-host of “Fox & Friends.” He joined the network as a contributor in 2014 and has been the host of Fox’s New Year’s coverage for years.

He served in the Army in Afghanistan and Iraq and at Guantánamo Bay, Cuba.

A Minnesota native, Mr. Hegseth graduated from Princeton University, where he was the publisher of The Princeton Tory, a conservative magazine, for which he wrote about seeing the statue of Saddam Hussein toppled in Baghdad in 2003.

“Conservative ideas have worked, do work and will continue to work,” Mr. Hegseth wrote. “The list is long: A strong military is absolutely essential to bringing long-term peace and stability to the world.”

He holds a master’s in public policy from the Harvard Kennedy School, according to Fox.

In 2019, Mr. Hegseth lobbied heavily on behalf of Chief Petty Officer Edward Gallagher, a member of the Navy SEALs who was acquitted of serious war crimes in Iraq. Mr. Trump reversed a demotion ordered as punishment, then fired the Navy secretary, whom Mr. Hegseth had aggressively criticized.

Mr. Hegseth defended Chief Gallagher on Fox News and spoke to Mr. Trump several times about the case. “From the beginning, this was overzealous prosecutors who were not giving the benefit of the doubt to the trigger-pullers,” he said.

Mr. Hegseth’s book, the New York Times best-seller “The War on Warriors: Behind the Betrayal of the Men Who Keep Us Free,” was published in June. “Our ‘elites’ are like the feckless drug-addled businessmen at Nakatomi Plaza, looking down on Bruce Willis’s John McClane in ‘Die Hard,’” Mr. Hegseth wrote in the book. “But there will come a day when they realize they need John McClane — that in fact their ability to live in peace and prosperity has always depended on guys like him being honorable, powerful and deadly.”

In his statement, Mr. Trump praised Mr. Hegseth’s book, which he said “reveals the left-wing betrayal of our warriors, and how we must return our military to meritocracy, lethality, accountability and excellence.”

But Mr. Hegseth is likely to run into opposition from senior military officials and perhaps lawmakers who have served in the military for his embrace of narratives by troops who ran afoul of military justice rules. A former Pentagon official from Mr. Trump’s first term questioned Mr. Hegseth’s lack of experience — other than serving in the military — and raised concerns about his ability to win Senate confirmation, even with a Republican majority in the chamber.

In a statement on Tuesday, Fox News called Mr. Hegseth “an exceptional host on ‘Fox & Friends’ and ‘Fox Nation’ and a best-selling author for Fox News Books for nearly a decade.”

“His insights and analysis, especially about the military, resonated deeply with our viewers and made the program the major success that it is today,” the statement said.

As a congressman, Mr. Ratcliffe fought on Mr. Trump’s behalf, helping to pursue investigations into Hunter Biden, the president’s son, and repeatedly criticizing the investigations into ties between Russia and Mr. Trump’s 2016 campaign.

Mr. Ratcliffe’s selection adds to the string of fierce Trump loyalists chosen so far for senior positions in the president-elect’s administration. But while Mr. Ratcliffe firmly backed Mr. Trump’s agenda as the director of national intelligence, he did not accede to every demand Mr. Trump made, something that could aid him as the Senate debates his confirmation.

His confirmation would most likely make Mr. Ratcliffe the most influential voice on intelligence matters in the next administration. Nominally, the C.I.A. director is subordinate to the Office of the Director of National Intelligence. But the C.I.A. director, with the power to appoint the senior spies stationed overseas and to conduct covert operations, arguably has more influence, and Mr. Trump has long viewed the C.I.A. job as more important.

Some lawmakers on Tuesday quickly praised the nomination, including Representative Mike Turner, the chairman of the House Intelligence Committee and a Republican from Ohio.

As C.I.A. director, Mr. Ratcliffe will help “counter the serious threats posed by China, Russia, Iran and North Korea,” Mr. Turner said.

When Mr. Ratcliffe was nominated to be the director of national intelligence in Mr. Trump’s first term, senators were initially hesitant to confirm him, seeing him as too partisan for the job, and he withdrew his nomination when it was initially offered.

Mr. Trump appointed Richard Grenell, who was the president’s combative ambassador to Germany and had little experience in collecting intelligence, as the acting director. A few months later, when Mr. Trump again floated the idea of Mr. Ratcliffe’s nomination, he was seen by senators as a more palatable choice.

As director of national intelligence, Mr. Ratcliffe warned about Chinese efforts to undermine Mr. Trump’s 2020 re-election campaign, but he and his subordinates also did not shy away from saying Russia was trying to denigrate Joseph R. Biden Jr., Mr. Trump’s 2020 challenger. Mr. Ratcliffe also exposed an Iranian plot to try to influence voters in Florida, which later led to indictments during the Biden administration.

Mr. Ratcliffe was deeply critical of how spy agencies looked at China. He argued that analysts had one standard for judging Russian influence operations and another for evaluating Chinese influence.

The Biden administration generally saw Iran and Russia as greater threats to conduct influence operations, but officials also said Mr. Ratcliffe had raised legitimate concerns. Officials in the current administration said they have worked to develop a single standard for evaluating influence operations.

As the director of national intelligence, Mr. Ratcliffe undertook some actions that critics saw as partisan.

At the end of his first administration, Mr. Trump and key aides sought to declassify information that they believed undermined Democratic views about Russian influence operations in the 2016 election. Mr. Ratcliffe, over the objections of the C.I.A., declassified some of the material that had been requested by Senator Lindsey Graham, Republican of South Carolina. (The material involved the Russians’ analysis of what they thought Hillary Clinton was planning to do in the 2016 election.)

Mr. Ratcliffe also declassified material sought by Senator Charles E. Grassley, Republican of Iowa, and others, about calls made by the retired Lt. Gen. Michael T. Flynn, before he became Mr. Trump’s first national security adviser.

But he also showed that he had limits. Some allies of Mr. Trump wanted Mr. Ratcliffe to release sensitive material gathered from intelligence files by Republicans on the House Intelligence Committee. The C.I.A. opposed the release. Mr. Ratcliffe reviewed the material and ultimately sided with the agency.