NATO secretary-general Jens Stoltenberg said on Sunday, June 19, that the war in Ukraine could last for years, but that the West “must not let up in supporting Ukraine, even if the costs are high, not only for military support but also because of rising energy and food prices.”

Yet polling indicates that support for Ukraine aid among Americans is slowly slipping as the conflict turns into a grinding battle of attrition that increasingly appears to favor the invading Russian forces. The Pew Research Center has found that a plurality of Americans no longer believe that the United States is “not providing enough assistance to Ukraine,” with the share who think that Washington is providing “too much assistance” rising from 7 percent to 12 percent between March and May.

The downturn in support has been particularly stark among Republicans. According to a Morning Consult poll taken in May, the share of GOP voters who say Washington is “doing too much” to halt Russia’s invasion of Ukraine has more than doubled from 13 percent to 27 percent between early March and mid-May, while the share of those who think the United States is “not doing enough” has dropped from 36 percent to 25 percent. These attitudes closely coincide with the mounting belief among Americans, according to YouGov/Economist polling from mid-March to mid-June, that Ukraine is losing. The share of Americans who think Russia will be the eventual winner of the conflict has reached its highest point since March at 29 percent.

The number of Americans who are explicitly against further aid to Ukraine, though still relatively small, has steadily risen in past months. This shift has been accompanied by a growing minority of Republican lawmakers and GOP candidates who have expressed skepticism over continued U.S. involvement in the Ukraine conflict. The result has been something of an avalanche effect: with each subsequent bill in support of Ukraine, a few more Republicans joined the side of the skeptics. This creeping dissent came to a head with the passage of President Joe Biden’s May request for $40 billion in weapons and economic aid to Ukraine, which drew opposition from as many as fifty-seven House Republicans.

In what could be remembered as a watershed moment for contemporary American foreign policy discourse, the conservative Heritage Foundation—long a proponent of what Frederick Jackson Turner famously described as a vigorous foreign policy—surprised its allies and opponents alike by taking a stance against the “bloated” bill, arguing that it suffered from a lack of strategic clarity and meaningful oversight.

Sen. Rand Paul (R-KY), supported by ten of his Republican colleagues, blocked the bill from being fast-tracked. “Kyiv would become the largest yearly recipient of U.S. military aid over the past two decades,” Paul said. “It is more than any other country spends on their entire military expenditures ... our total aid to Ukraine will almost equal the entire military budget of Russia.” Paul sought to modify the $40 billion aid package with the appointment of an inspector general to oversee how the money is being spent. Paul was overruled by Senate Minority Leader Mitch McConnell (R-KY), who worked with Senate Majority Leader Chuck Schumer (D-NY) to get the mammoth aid bill over the finish line without any amendments.

But what exactly is motivating the opposition to Ukraine aid among some Republicans and GOP candidates?

“A growing chorus of voices on the Right are driving opposition to giving Ukraine the assistance it needs. You even see these sentiments emanating from the Heritage Foundation, which is shocking,” said Melinda Haring, deputy director of the Atlantic Council’s Eurasia Center. “There’s long been an isolationist wing within the GOP that wants to focus on U.S. priorities, pointing to the disasters in Afghanistan and Iraq as evidence of the stupidity of nation building. They aren’t wrong about Afghanistan and Iraq, but supporting Ukraine from Russia’s unprovoked attack is hardly nation building,” Haring added.

These Congressional Republicans, whose growing ranks include Rep. Thomas Massie (R-KY), Sen. Josh Hawley (R-MO), Rep. Marjorie Taylor Greene (R-GA), Sen. Marsha Blackburn (R-TN), and Sen. Mike Lee (R-UT), have been criticized as “isolationists” and “anti-Ukraine” by their detractors within and without the GOP. “Honestly there is an isolationist wing within the party that’s traditionally been there,” Rep. Michael McCaul told the Washington Post.

Still, others have questioned the use of these labels. “It is absolutely unfair to characterize lawmakers who oppose sending more U.S. taxpayer dollars to Ukraine or want to see greater oversight of our aid to that country as anti-Ukraine,” said Will Ruger, former President Donald Trump’s nominee for ambassador to Afghanistan and vice president for research and policy at the Charles Koch Institute. “These legislators just happen to be pro-American and have a different view than others about how best to support U.S. national interests in this case and how they read the cost-benefit analysis of such efforts. The charge of “isolationism” is now and has always been just a pejorative slur used against those who have perfectly legitimate reasons for opposing any particular U.S. intervention or activism. It is simply trying to police who is a legitimate voice and using the slur to marginalize voices of realism and restraint.”

Conservative Ukraine detractors are informed by a wide range of foreign and domestic concerns that are difficult to distill into a unitary set of ideas. Author and politician J.D. Vance, fresh off his win in the Ohio Senate primary election, has become one of the loudest conservative voices of Ukraine skepticism. “Using American power to do the dirty work of Europe is a pretty bad idea,” said Vance at a Washington conference in April. “We don’t have that many non-insane people in Washington. I need you to be some of them.” Vance’s message is resonating with a part of the GOP base that sees Washington policymakers as overly preoccupied with a far-away foreign conflict at a time when they should be focusing their undivided attention on the multiple crises gripping American life. “Some Republicans understand that the politics have changed post-Trump,” said a foreign policy expert familiar with the thinking of Congressional Republicans. “The Republican base was always realist, but the edifice is still somewhat interventionist. The old pre-WWI roots of American republicanism and anti-interventionism are coming back, and might argue, for good, especially after the disastrous last thirty years.”

Haring said she supports Paul’s proposal for an inspector general to oversee Ukraine aid spending, citing a growing concern among watchdogs that the funds making their way to Kyiv could be misappropriated by local authorities. But there is an attitude among some conservatives in Washington DC that the inspector general proposal and other initiatives to draw soft boundaries around Ukraine spending do not sufficiently address the underlying long-term problems in U.S. foreign policy. “That would just add an additional tier of bureaucracy,” the foreign policy expert said, adding that the establishment of sub-departments and specialized commissions within the State Department and Pentagon has only served to push U.S. foreign policy in a more “interventionist” direction over time.

The Ukraine conflict has become a rallying point for a growing wing of the conservative movement espousing a commitment to realism and restraint, broadly defined as the position that Washington should abandon ideas of liberal universalism in favor of a foreign policy grounded in realist thought. “Realism and restraint is a much stronger force now than the last time we saw green shoots of Republican opposition to primacy in the 90s that didn’t last after 9/11. There is a larger body of ideas circulating within this paradigm and the approach is more institutionalized, even on the Right,” said Ruger.

For these GOP lawmakers and candidates, the implications of realism and restraint extend beyond the immediate conflict unfolding in Ukraine. “I think this opposition isn’t just about these legislators putting on their green eyeshades or worrying about escalation with a nuclear Russia,” said Ruger. “It is also about a growing block of Republican politicians who are explicitly questioning establishment bromides and rethinking U.S. foreign policy more broadly with greater realism in mind. So, in one sense it is about the particular case of Ukraine, how we got here, and how engaging stacks up relative to our interests. But in another sense, it is about something broader and how the particular fits into it.”

The realism and restraint faction within the GOP is best conceived not as a concrete party platform, but as a loose coalition organized around shared attitudes about America’s place in a changing world order. “While this group doesn’t agree on everything, especially how to deal with the relative rise of China, they have different assumptions and views about the nature of the world that is emerging and America’s proper role within it than many of their, often older, colleagues,” said Ruger. “So, they don’t reflexively think of our allies as “sacred” the way Joe Biden does and even many other Republican voices do. They don’t think as idealistically and in as Manichean a fashion as we see with many Democrats and saw with many Bush-era Republicans. They don’t see threats the same way.”