A win by Vice President Kamala Harris could be expected to bring a continuation of current policy, though with Republican opposition and growing war fatigue among the US public there are concerns in Europe that support would wane.

Trump’s appetite for imposing tariffs on US partners also is causing worry in a Europe already struggling with sluggish economic growth. But it’s not just the possibility of a second Trump presidency that has the continent anxious about tougher times ahead.

European officials believe US priorities lie elsewhere, no matter who wins. The Middle East is top of President Joe Biden‘s list right now, but the long-term priority is China.

“The centrality of Europe to US foreign policy is different than it was in Biden’s formative years,” said Rachel Tausendfreund, a senior research fellow at the German Council on Foreign Relations in Berlin. “And in that way, it is true that Biden is the last trans-Atlantic president.”

The US will continue to pivot toward Asia, she said. “That means Europe has to step up. Europe has to become a more capable partner and also become more capable of managing its own security area.” Germany’s defence minister, Boris Pistorius, remarked when he signed a new defense pact with NATO ally Britain that the US will focus more on the Indo-Pacific region, “so it is only a question of, will they do much less in Europe because of that or only a little bit less”. Ian Lesser, a distinguished fellow at the German Marshall Fund in Brussels, said that “above all, Europe is looking for predictability from Washington,” and that’s in short supply in a turbulent world in which any administration will face other demands on its attention. “But the potential for disruption is clearly greater in the case of a potential Trump administration.”

“There is an assumption of essential continuity” under Harris that’s probably well-founded, he said, with many people who have shaped policy under Biden likely to remain. “It’s very much the known world, even if the strategic environment produces uncertainties of its own.”

While both the US and Europe have been increasingly focused on competition with Asia, the ongoing war in Europe means “the potential costs of a shift away from European security on the American side are very much higher today than they might have been a few years ago,” Lesser said. Europe’s ability to deal with that depends on how quickly it happens, he said.

Europe’s lagging defence spending irked US administrations of both parties for years, though NATO members including Germany raised their game after the 2022 invasion of Ukraine. NATO forecasts that 23 of the 32 allies will meet its target of spending 2% or more of gross domestic product on defense this year, compared to only three a decade ago.

During his 2017-2021 term, Trump threatened to abandon “delinquent” countries if they weren’t paying their “bills”. In campaigning this time, he suggested that Russia could do what it wants with them.

His bluster has undermined trust and worried countries nearest to an increasingly unpredictable Russia, like Estonia, Latvia, Lithuania and Poland.

Europeans see the war in Ukraine as an existential challenge in a way the United States eventually may not, even with some signs of war fatigue emerging in Europe itself.

If Trump wins, “there’s every indication that he has no interest in continuing to support Ukraine in this war” and will push quickly for some kind of cease-fire or peace agreement deal that Kyiv may not like and Europe may not be ready for, Tausendfreund said. “And there is also just no way that Europe can fill the military gap left if the US were to withdraw support.”

“Even with a Harris administration there is a growing, changing debate – frankly, on both sides of the Atlantic – about what comes next in the war in Ukraine, what is the end game,” Lesser said.

Biden emphasised the need to stay the course in Ukraine during a brief recent visit to Berlin when he conferred with German, French and British leaders.

“We cannot let up. We must sustain our support,” Biden said. “In my view, we must keep going until Ukraine wins a just and durable peace.”

The times he has lived through have taught him that “we should never underestimate the power of democracy, never underestimate the value of alliances,” the 81-year-old Biden added.

German President Frank-Walter Steinmeier, who bestowed Germany’s highest honour on Biden for his service to trans-Atlantic relations, hopes Biden’s compatriots are listening.

“In the months to come, I hope that Europeans remember: America is indispensable for us,” he said. “And I also hope that Americans remember: Your allies are indispensable for you. We are more than just other countries’ in the world -we are partners, we are friends.”

Whoever wins the White House, the coming years could be bumpy.

“Whatever the outcome next week, half of the country will go away angry,” Lesser said, noting there’s “every prospect” of divided government in Washington. “Europe is going to face a very chaotic and sometimes dysfunctional America.”