The steamy and stifling Washington humidity poaching European diplomats through their business suits wasn’t the only cloud hanging over this week’s NATO summit. It had already been clear for weeks that the gathering, held in DC to commemorate the alliance’s founding here 75 years ago, would be shadowed by questions about the upcoming US presidential election. And that was before President Joe Biden’s disastrous June 27 debate, which made it increasingly likely that NATO leaders would soon be dealing with Donald Trump, not Biden, in the White House.

“The debate between Biden and Trump is sort of an elephant in the room,” Rachel Rizzo, a senior fellow and expert on NATO at the Atlantic Council, told Vox. “And I think if you are a European ally, and you watched that debate, you’re probably concerned about Biden’s ability to win the election.”

Speaking with reporters on Thursday, national security adviser Jake Sullivan denied that any allies had expressed concerns about Biden’s performance in office. On the contrary, he said, he had heard “a drumbeat of praise for the United States, but also for President Biden, personally, for what he’s done to strengthen NATO.” Reporting from multiple news outlets suggests otherwise, but whatever misgiving these allies might have, they have little incentive to bring them up in public.

“No European leader is going to come out and disparage the US president,” Rizzo noted. “It doesn’t help to come to Washington and tell everyone you’re freaking out about this.”

Any hopes Biden would be able to use the summit to reassure his critics about his fitness for the campaign were dashed on Thursday afternoon when he accidentally introduced President Volodymyr Zelenskyy of Ukraine as “President Putin” — the man currently trying to kill Zelenskyy.

Whether he stays on the ticket or not, it’s looking increasingly likely that Biden, a longtime fixture of the US foreign policy establishment and a longtime supporter of the transatlantic alliance, may only have a few months left in office.

As Zelenskyy put it somewhat obliquely in a speech in Washington on Tuesday, “Let’s be candid and frank. Now everyone is waiting for November.”

Trump’s skepticism about the value of long-term alliances, which he largely sees as opportunities for countries to free-ride on American security guarantees and defense spending, was arguably the most consistent through line of his foreign policy as president. The prospect of his return has stoked fear about the future of those alliances. The Japanese press has even coined a word for this anxiety: “moshitora,” or “what if Trump?”

There has long been a special place in Trump’s ire for NATO, which he has called “obsolete” and “as bad as NAFTA.” (NAFTA, in Trump’s protectionist view, was about as bad as international deals get.) Trump threatened on several occasions as president to pull out of the alliance, and advisers say he likely would have if he had been reelected in 2020.

Trump’s main complaint was that a significant number of NATO members had long failed to meet the alliance’s target of spending 2 percent of their GDP on defense. That complaint wasn’t a new one — former presidents Barack Obama and George W. Bush voiced the same complaint — though Trump’s comments suggested misleadingly that these countries owed money toNATO, or even to the US. (They didn’t and don’t — the target, which is nonbinding, refers to countries’ spending on their own defense.)

More recently, Trump boasted that he would let Russia “do whatever the hell they want” to countries that “didn’t pay.” This week, Trump underlined NATO leaders’ anxieties by meeting with Hungary’s Prime Minister Viktor Orbán, the alliance’s principal gadfly and Putin defender.

The “moshitora”in Washington this week has created insecurity for an alliance that would otherwise have some reason for swagger on its 75th birthday, though for a very unfortunate reason. Throughout the war on terror, NATO struggled to define its post-Cold War mission amid long-term, long-range deployments, such as Afghanistan, for which it often felt ill-suited. Just five years ago, French President Emmanuel Macron, hardly a Trumpian isolationist, described the alliance as “brain-dead.”

All that changed with Russia’s invasion of Ukraine, which brought the alliance back to its original core mission: protecting Europe from Russia. As Sen. James Risch (R-ID), ranking member of the Senate Foreign Relations Committee, put it on Wednesday, before 2022, “​​NATO had become stodgy. We’d forgotten what it was formed for. NATO was formed for the exact circumstance we find ourselves in today.”

The most obvious post-war change for the alliance is the addition of two new flags outside its headquarters in Brussels: Sweden and Finland, who joined in the wake of Russia’s invasion of Ukraine after decades of neutrality. The allies have also gone a long way toward addressing Trump’s principal complaint. In 2024, 23 of the 32 members are expected to spend more than 2 percent of their GDP on defense, up from just three in 2014. Trump’s allies have taken some credit for this, as have Biden administration officials. But in truth, most of the credit probably belongs to Vladimir Putin for reminding NATO’s member-states why it exists.

In recent months, Trump has somewhat softened his rhetoric on NATO, saying he would “100 percent” stay in the alliance, as long as European countries “play fair.” But he still seems poised to undermine what has become NATO’s overriding priority: aiding Ukraine in its war with Russia. Trump reportedly plans to pressure Ukraine into negotiations with Russia by threatening to withhold US military aid. Without it, the war wouldn’t end, but Ukraine’s defenses may not be able to hold out.

At the summit in Washington this week, which took place in the wake of a devastating missile attack on a children’s hospital in Kyiv, Ukraine got some major new aid pledges, including dozens of new air defense batteries and the long-awaited announcement that US-made F-16 fighter jets would be on their way to the country from Denmark and the Netherlands. Ukraine was not offered full NATO membership but the summit communique did affirm its “irreversible path” to membership, which is stronger language than has been used before.

NATO policymakers have been working to “Trump-proof” some aspects of aid to Ukraine, such as setting up a new command center in Germany to coordinate military aid and the training of Ukrainian troops. But the strains on Ukraine’s defenses caused by Congress’s monthslong delay in authorizing new aid this year made it clear how much the international assistance effort still relies on US support.

As I reported around the summit this week, it became clear that the talk was less about “Trump-proofing” — likely impossible — than about making a pitch for the alliance and its mission in terms that can be seen as MAGA-friendly. If not quite acceptance, it seemed officials had at least reached the bargaining stage when it came to a Trump return.

At a reception hosted by the European Union on Tuesday night, Oleksandr Kamyshin, Ukraine’s minister of strategic industries, suggested that what’s good for Ukraine is also good for American business, whoever is occupying the White House. “I’ve heard that Republicans stand for the defense industry. We’re bringing value to the defense industry of the US,” he said.

At the same event, Laurynas Kasčiūnas, Lithuania’s defense minister, said, “There are many directions where we can work with a future possible Trump administration if it happens.” A worse strategy, he suggested, would be “if we try to build in Europe a moral wall against Trump. We need to be calm and find ways to communicate with him.” He also noted that Trump’s hostility to the Euro-Atlantic mission was often more talk than practice. It was under Trump, after all, that US troops were first deployed to Lithuania, on Russia’s border.

One senior NATO official, speaking on background in Washington this week, suggested that the recent boost in defense spending by NATO countries might defuse some of the tension.

“Calling out European allies and Canada to spend more on defense was warranted,” the official said. “Raising the issue of defense spending was not exclusive to the Trump administration. [Now] we are in a different place. We have turned a corner and I think we have several examples to show that.”

Zelenskyy notably spoke at the Ronald Reagan Presidential Foundation and was introduced by Senate Minority Leader Mitch McConnell, though this felt like an appeal to an internationalist Republican party that no longer exists.

Whatever your views on the former president, it’s hard to fault European leaders for their Trump-friendly appeals this week. There’s little other option.

As Danish Prime Minister Mette Frederiksen put it on a panel at NATO’s public forum on Wednesday, referring to the US complaints about European reliance on American military power: “We have to admit, from a European perspective, that we were depending on you. We still depend on you. Never leave us.”