The war in the Middle East, anxiety about the commitment of the U.S., and divisions in Europe are worrying Kyiv that aid from the West may wane.Clearly anxious, President Volodymyr Zelensky of Ukraine went in person this week to see NATO defense ministers in Brussels, worried that the war between Israel and Hamas will divert attention — and needed weapons — from Ukraine’s long and bloody struggle against the Russian invasion.American and NATO officials moved to reassure Mr. Zelensky, pledging another $2 billion in immediate military aid. But even before the war in the Mideast began last week, there was a strong sense in Europe, watching Washington, that the world had reached “peak Ukraine” — that support for Kyiv’s fight against Russia’s invasion would never again be as high as it was a few months ago.The new run for the White House by former President Donald J. Trump is shaking confidence that Washington will continue large-scale support for Ukraine. But the concern, Europeans say, is larger than Mr. Trump and extends to much of his Republican Party, which has made cutting support for Ukraine a litmus test of conservative credibility.Even in Europe, Ukraine is an increasingly divisive issue. Voters in Slovakia handed a victory to Robert Fico, a former prime minister sympathetic to Russia. A vicious election campaign in Poland, one of Ukraine’s staunchest allies, has emphasized strains with Kyiv. A far right opposed to aiding Ukraine’s war effort has surged in Germany, where Chancellor Olaf Scholz is struggling to win voters over to his call for a stronger military.“I’m pessimistic,” said Yelyzaveta Yasko, a Ukrainian member of Parliament who is on the foreign affairs committee. “There are many questions now — weapons production, security infrastructure, economic aid, the future of NATO,” she said, but noted that answers to those questions had a timeline of at least five years.President Volodymyr Zelensky of Ukraine, right, talking with Defense Secretary Lloyd J. Austin III on Wednesday at a NATO meeting in Brussels.Olivier Matthys/Agence France-Presse — Getty Images“We have been fighting for 600 days,” she added, “and I don’t see the leadership and planning that is required to take real action — not just statements — in support of Ukraine.”Even more depressing, Ms. Yasko said at a recent security forum in Warsaw, is the way domestic politics are “instrumentalizing Ukraine.”“Opinion polls show the people still support Ukraine,” she said, “but politicians start to use Ukraine as a topic to fight each other, and Ukraine becomes a victim.”“I’m worried,” she continued. “I don’t like the way my country is used as a tool.”The previous bipartisan support for Ukraine in the United States no longer seems to hold. “There’s less pushback against the anti-Ukrainian stuff already out there,” said Toomas Hendrik Ilves, the former president of Estonia, mentioning the Republican right wing and influential voices like Elon Musk. “It’s dangerous.”Should Washington cut its aid to Ukraine, deciding that it is not worth the cost, top European officials, including the European Union’s head of foreign affairs and security policy, Josep Borrell Fontelles, openly acknowledge that Europe cannot fill the gap.He was in Kyiv, Ukraine’s capital, when Congress excluded support from Ukraine in its temporary budget deal. “That was certainly not expected, and certainly not good news,” Mr. Borrell told a summit meeting of E.U. leaders this month in Spain.European Union’s head of foreign affairs and security policy, Josep Borrell Fontelles, right, with Dmytro Kuleba, Ukraine’s foreign minister, this month in Kyiv, Ukraine’s capital.Ukraine Ministry of Foreign Affairs, via EPA, via Shutterstock“Europe cannot replace the United States,” he said, even as it proposes more aid. “Certainly, we can do more, but the United States is something indispensable for the support to Ukraine.” That same day, President Vladimir V. Putin of Russia said that without Western aid, Ukraine could not survive more than a week.European leaders have pledged to send more air-defense systems to Ukraine to help fend off a possible new Russian air campaign targeting energy infrastructure as winter looms. Prime Minister Mark Rutte of the Netherlands said on Friday that his country would send additional Patriot missiles, which have proved effective in defending the skies over Kyiv, according to Mr. Zelensky’s office.At the same time, European vows to supply one million artillery shells to Ukraine by March are falling short, with countries supplying only 250,000 shells from stocks — a little more than one month of Ukraine’s current rate of fire — and factories still gearing up for more production.Adm. Rob Bauer, who is the chairman of the NATO Military Committee, said in Warsaw that Europe’s military industry had geared up too slowly and still needed to pick up the pace.“We started to give away from half-full or lower warehouses in Europe” to aid Ukraine, he said, “and therefore the bottom of the barrel is now visible.”Even before the outbreak of hostilities in the Middle East, a senior NATO official said that the mood about Ukraine was gloomy. Still, the official said that the Europeans were spending more on the military and that he expected Congress to continue aid to Ukraine, even if not the $43 billion authorized previously.Malcolm Chalmers, the deputy director of the Royal United Services Institute, a London-based defense research institution, said a key issue now is Ukrainian will and resources in what has become a war of attrition. “It’s not really about us anymore, it’s about them,” he said. “The issue is Ukrainian resilience.”Ukrainians will quietly admit to difficulties with morale as the war grinds on, but they see no option other than to continue the fight, whatever happens in the West.Soldiers with the 128th Brigade repairing a broken down Carnation, a self-propelled artillery piece, before taking it back to the front line in September in the Zaporizhzhia region of Ukraine.Lynsey Addario for The New York TimesBut some say that they are fearful that President Biden, facing what could be a difficult re-election campaign against Mr. Trump, will try to push Kyiv to get into negotiations for a cease-fire with Russia by next summer, to show that he is committed to peace.That worry is likely to be exaggerated, American officials suggest, given Mr. Biden’s continuing strong support for Ukraine, which is echoed in American opinion polls. But there remains confusion about any end goal that does not foresee Ukraine pushing all Russian troops out of sovereign Ukraine, or any clear path to negotiations with a Russia that shows no interest in talking.As Gabrielius Landsbergis, the foreign minister of Lithuania, said at the Warsaw security forum, the mantra “as long as it takes” fails to define “it,” let alone “long.” For him, “it” should mean driving the invading Russians out of all of Ukraine, including Crimea, which Moscow illegally annexed in 2014.In private, at least, other European officials consider that highly unlikely.Carl Bildt, the former Swedish prime minister and foreign minister, suggested that NATO’s 75th anniversary summit meeting next summer in Washington will be tense because of Ukraine, as it will come at the height of the American presidential campaign. Any invitation for Ukraine to join NATO is likely to help Mr. Trump, the presumptive Republican candidate, Mr. Bildt said.But while many worry about the possibility of declining American support for Ukraine, the potential for backsliding is not limited to the United States, as the costs of the war are more deeply felt in Europe.In its campaign in Poland, for elections this weekend, the governing Law and Justice Party has complained angrily that Ukrainian grain exports are flooding the Polish market, damaging the farmers who are a key element of the party’s support and underlining the implications for Polish agriculture should Ukraine join the European Union.Mr. Zelensky responded that “it is alarming to see how some in Europe, some of our friends in Europe, play out solidarity in a political theater — making a thriller from the grain.”Grain stored in Leszczany, Poland, in April.Maciek Nabrdalik for The New York TimesThe Polish government, fighting for votes with parties farther to the right, then said it would cease military aid to Ukraine, even though it has already provided an enormous amount early in the war.Anti-Russian sentiment is a given in Poland, but the animosity toward Germany, an E.U. and NATO ally, was striking, too, said Slawomir Debski, the director the of Polish Institute of International Affairs.He described the campaign as “very dirty,” with wild accusations playing on strong anti-German, anti-Russian, anti-European Union sentiments, combined with growing tensions with Ukraine.It was all a sharp contrast to Poland’s embrace of Ukrainian refugees and important early provision of tanks, fighter jets and ammunition just last year.“I warned many people, including the Americans, that this government is being accused of doing too much for Ukraine, so be careful,” Mr. Debski said.Michal Baranowski, a Pole who is the managing director for the German Marshall Fund East, said he was “disheartened because Polish political leaders know we need to stay the course in Ukraine, but they are letting emotions and politics get the better of them.”Polish division, however political, does not stay in Poland, Mr. Baranowski warned. “The effect of this on the United States and the Republican Party is terrible,” he said.Constant Méheut More