LONDON — President Trump has always relished throwing European leaders off balance, antagonizing allies, embracing insurgents and setting off a frantic contest for how best to deal with him. Now, as Europe undergoes dizzying political changes of its own, it is throwing Mr. Trump off balance.
In London for a NATO summit meeting, Mr. Trump was subjected to a rare tongue-lashing on trade and terrorism by President Emmanuel Macron of France, who dismissed his attempt to lighten the mood with a curt, “Let’s be serious.” Earlier in the day, Mr. Trump held his own tongue about British politics, heeding Prime Minister Boris Johnson’s plea not to barge into Britain’s election at the 11th hour.
For a president who prides himself on being the Great Disrupter, it was a startling turnabout, one that underscored how Europe’s shifting landscape — with an ambitious president in France, a lame-duck leader in Germany and a breakaway populist in Britain — has scrambled the calculus for Mr. Trump.
For now, at least, Mr. Macron has replaced Chancellor Angela Merkel of Germany as Mr. Trump’s chief antagonist on the Continent. The French president’s assertion last month that NATO was in a state of “brain death” angered both Mr. Trump and Ms. Merkel, and has created an improbable, if perhaps fleeting, alignment between those two leaders who spent much of the last three years on opposite poles.
As for Mr. Johnson, his most natural ally, Mr. Trump bridled almost visibly as he tried to stay out of the election on Dec. 12. “I don’t want to complicate it,” he said, in a grudging admission that he is so unpopular in Britain that a full-throated endorsement of the prime minister could backfire.
When NATO decided to mark its 70th anniversary with a meeting in London, the goal was to limit the potential for disruption from Mr. Trump if it were held in Washington. As luck would have it, the summit wound up falling in the final 10 days of an election campaign in which Mr. Trump has been a recurring issue.
“Trump is in an awkward position right now,” said Lewis A. Lukens, who served as acting ambassador to Britain in the first months of the Trump presidency. “His instincts are to pull Johnson close, but he will have been told by his team that any intervention would be counterproductive.”
Since Mr. Trump took office, Europeans have labored to adjust to his prejudices and preferences. They praised him for his success in calling on NATO members to increase their payments to the alliance, flattered him with invitations to military parades, as Mr. Macron once did, and stoically bore his attacks on their trade surpluses with the United States, like Ms. Merkel has.
But Europe is changing, too, with Britain seeking to leave, Ms. Merkel nearing the end of her tenure, and Mr. Macron staking his claim to European leadership with a vision of the future that depends less on the United States. His criticism of NATO is inevitably, if indirectly, a criticism of Mr. Trump and his “America First” policy.
As Europe changes, Mr. Trump is finding that he has to recalibrate his approach. With his own re-election campaign looming, he also wants credit for what he views as his foreign policy accomplishments, including NATO. On the first day of his trip to London, it made for some remarkable political theater.
The president who once threatened to pull the United States out of NATO suddenly emerged as the alliance’s defender. The president who once exchanged a death-grip handshake with Mr. Macron sat by wordlessly while his much-younger counterpart lectured him on the need to fight the Islamic State. The president who championed Brexit and hectored Mr. Johnson’s predecessor, Theresa May, about her deal-making skills suddenly had nothing to say about it.
Asked about the British election, Mr. Trump resorted to talking about how his campaigning had helped Republican gubernatorial candidates in Kentucky and Louisiana — never mind that both men lost — before implicitly acknowledging that his involvement in Britain would probably not help.
“I love this country,” Mr. Trump said. “I love a lot of countries, but I’m representing the U.S. They may not like me because I’m representing us, and I represent us strong.”
The president has always viewed statecraft as both highly personal and strictly transactional, which makes some experts wary of drawing overly broad conclusions from Mr. Trump’s early performance in London. His clash with Mr. Macron, they said, may reflect as much personal pique about Mr. Macron’s assertive style as basic disagreements over the future of NATO.
“At the moment, Macron has replaced Merkel as his nemesis,” said Thomas Wright, the director of the Center on the United States and Europe at the Brookings Institution, “but I could see them working together in a few months.”
“There is a general alignment of their critiques on NATO,” Mr. Wright continued. “Macron says NATO should focus on terrorism; Trump says NATO should focus on terrorism and the Middle East. Macron says Russia is not such a big threat; Trump says Russia is not such a big threat.”
If anything, he said, other NATO members have worried that the two leaders would ally too closely behind a vision for the alliance that dials back the clock — away from strategic rivals like China and toward the quagmires of the Middle East.
Mr. Trump is scheduled to meet Ms. Merkel on Wednesday, and history suggests it will be a far less tempestuous encounter than he had with Mr. Macron. Still, there is little evidence that he will develop any closer ties with the chancellor in her waning years than he did with Mrs. May.
Likewise, Mr. Trump’s newfound discretion on British politics will probably last only until Dec. 12, when Britons go to the polls, if that long. If Mr. Johnson is successful in winning a parliamentary majority and takes Britain out of the European Union, he will be more dependent than ever on his relationship with Mr. Trump, particularly since he has sold Brexit on the promise that he can cut a lucrative trade deal with the United States.
Mr. Johnson’s Labour Party opponent, Jeremy Corbyn, is trying to stoke fears that Mr. Trump will demand that a Conservative-led government open up Britain’s revered National Health Service to American drug companies.
On his last trip to London, Mr. Trump declared that “everything will be on the table” in a negotiation, including the N.H.S., before walking back his comments the following day. On Tuesday, Mr. Trump said he did not even know how those rumors got started.
“We have absolutely nothing to do with it, and we wouldn’t want to,” he said. “If you handed it to us on a silver platter, we’d want nothing to do with it.”
Even the ceremonial parts of Mr. Trump’s schedule attested to a changing of the guard. Before attending a reception given by Queen Elizabeth II at Buckingham Palace on Tuesday evening, the president and First Lady Melania Trump visited Prince Charles and his wife, the Duchess of Cornwall, at their residence, Clarence House.
Prince Charles has assumed a more central role in the royal family’s affairs in the aftermath of the scandal involving Prince Andrew’s ties with the disgraced financier, Jeffrey Epstein. Prince Andrew, who had withdrawn from public life, was conspicuously absent from the festivities on Tuesday.
“I don’t know Prince Andrew, but it’s a tough story,” said Mr. Trump, who was photographed with the prince during his state visit to London earlier this year and at Mar-a-Lago, his Palm Beach estate, nearly two decades ago.