Ohio Sen. J.D. Vance's opposition to more U.S. aid for Ukraine is stoking anxiety among Kyiv's supporters about sustained U.S. support and Ukraine's ability to fend off Vladimir Putin's invasion.
"I do not think that it is in America's interest to continue to fund an effectively never-ending war in Ukraine," Vance said during a speech in May, adding "we've done more than our fair share."
Although Vance's isolationist approach to foreign policy has even vexed members of his own party, he has candidly voiced his skepticism since the earliest days of the conflict.
"I gotta be honest with you, I don't really care what happens to Ukraine one way or another," Vance said in February 2022, amid an explosion of bipartisan support for country in the immediate aftermath of Russia's invasion.
MORE: US to send additional $2 billion in Ukraine aid, Blinken saysTwo U.S. officials and a European official tell ABC News they see Donald Trump's decision to pick Vance as his running mate as a clear sign the former president intends to double down on his "America First" vision if he wins a second term by disengaging from international concerns.
They expressed concern that if Trump, who has described Ukraine as a burden, is able to cut off aid to the country, Ukrainian troops may be unable to hold current lines and Kyiv's position at any negotiation table would be severely weakened.
In April, Vance broke with Senate Republican leaders to vote against a foreign aid package that included nearly $61 billion for Ukraine, asserting Moscow's threat to global stability had been overstated.
"Vladimir Putin is not Adolf Hitler. It doesn't mean he's a good guy, but he has significantly less capability than the German leader did," Vance said in a speech on the Senate floor.
"If Ukraine thinks that it's getting another $60 billion supplemental out of the United States Congress, there's no way," he later told reporters.
MORE: Senate passes $95B foreign aid package for Ukraine, Israel and Taiwan: What's next?Vance has also defended his pessimistic outlook on Ukraine's ability to triumph over Russia, calling himself a "realist."
In an April op-ed in the New York Times titled "The Math on Ukraine Doesn't Add Up," Vance argued that the U.S. could not possibly provide enough munitions to Ukraine to turn the tides of the war and called Ukraine's President Volodymyr Zelenskyy's goal of restoring the country to its 1991 boundaries "fantastical."
At the Munich Security Conference in February, Vance also said that focusing on Ukraine was distracting Washington from confronting other challenges such as China.
"There are a lot of bad guys all over the world. And I'm much more interested in some of the problems in East Asia right now than I am in Europe," Vance said.
But despite Trump and Vance's apprehension on assistance for Ukraine, many of their fellow Republicans have so far remained steadfast in their support.
In April, South Carolina Republican Sen. Lindsey Graham, a hawkish conservative, called Vance's arguments against assistance for Ukraine "garbage."
"I challenge J.D. Vance to go to Ukraine and get a briefing from the Ukrainian military and talk to the Ukrainian people," he said in a televised interview.
In an interview with Punchbowl News earlier this month, Senate Minority Leader Mitch McConnell -- one of Ukraine's most influential allies on Capitol Hill -- predicted that future support for Kyiv would depend not only on the outcome of the election in November, but also on whether Ukraine makes progress on the battlefield in the coming months.
"The conflict over the summer and how it is perceived to turn out is extremely important in answering the question inevitably coming up in democracies -- can they win?" McConnell said.