As President Volodymyr Zelensky of Ukraine stood at a lectern in the Capitol on Tuesday pleading with senators to quickly approve more aid for his country’s war against Russian invaders, Senator Lindsey Graham, Republican of South Carolina, delivered a blunt message.
“Here’s the problem,” Mr. Graham, a defense hawk who has been a champion of aiding Kyiv, recalled saying to Mr. Zelensky. “It’s got nothing to do with you.”
Mr. Graham went on to explain the harsh political reality that has blocked congressional approval of more American help for his embattled nation: The dispute is not over the merits of that fight at all. Republicans have changed the subject to an intractable domestic political dispute over clamping down on migration on the United States border with Mexico.
“I said, ‘You’ve done everything anybody could ask of you,’” Mr. Graham said later, recounting his exchange with the Ukrainian president. “‘This is not your problem here.’”
But it was a problem for Mr. Zelensky, whose visit to Capitol Hill and the White House failed to snap a Republican filibuster of a $110.5 billion emergency spending bill that includes $50 billion more in security aid for Ukraine. He made the case that supporting Kyiv would protect the West by preventing President Vladimir V. Putin of Russia from seizing more of Europe — only to be told by Republicans that that was beside the point.
His visit on Tuesday Capitol Hill was a vivid departure from Mr. Zelensky’s previous trips. A year ago, he was largely hailed by lawmakers as a hero. They invited him to address a joint meeting of Congress and capped off his trip by overwhelmingly approving nearly $50 billion to arm and aid his nation.
This time, with American support for sending aid to Ukraine deteriorating, particularly among G.O.P. members of Congress, the reception was markedly frostier. Some Republican senators made a point of doing a media tour preemptively criticizing Mr. Zelensky’s visit, and complained that he was coming at all.
“We’re hearing from the president of Ukraine again, but we’ve yet to hear from our own president about the border, our border,” said Senator Eric Schmitt, Republican of Missouri.
Mr. Zelensky made no public remarks at the Capitol, where he was essentially sidelined from the discussion. He did not attempt to involve himself in the domestic political dispute standing in the way of aid for his country.
“He simply said, ‘I know that I should not be involved’” in the discussions about the border, Senator Mike Rounds, Republican of South Dakota, said. “He made it clear that he understood that that was an issue. He was there to talk about their needs. And he did a very good job of not getting involved, not being pulled into the discussion.”
In the meantime, bipartisan talks in the Senate aimed at breaking the impasse on immigration policy have deteriorated, and lawmakers are openly talking about the likelihood that they will leave Washington for the holidays without passing aid for Ukraine.
“It is practically impossible” for Congress to pass a bill on Ukraine and border security before the holidays, said Senator Mitch McConnell, Republican of Kentucky, the minority leader who has been a leading champion of backing Kyiv in its war against Russia.
Senator Chuck Schumer of New York, the majority leader, said a stringent House-passed border measure championed by conservative hard-liners was dead on arrival in the Democrat-controlled Senate. “But if Republicans show they’re serious about meeting us in the middle, we are willing to meet them in the middle,” he said.
He said some G.O.P. lawmakers were simply “unwilling to budge” on their border demands.
“Unfortunately, it may seem the case that these are both excuses, and they really want to kill funding for Ukraine and never had any intention of passing it,” Mr. Schumer said. “That’s not true of all Republicans — but too many.”
Karoun Demirjian, Kayla Guo and Robert Jimison contributed reporting.
