President Donald Trump set his sights on the NATO alliance long before he took the oath of office. “NATO benefits Europe far more than it does the U.S.,” the president wrote in 2016. When pressed by a New York Times reporter whether, as president, he would come to the “immediate military aid” of NATO allies in the Baltics if Russia invaded, Trump said that would be contingent only on whether those states had “fulfilled their obligation to us.” As president, he has continued to question the value of NATO, even as his Cabinet officials unequivocally back the Atlantic alliance and his administration pursues admirably hawkish policies toward Russia.

The president’s reflexive defenders lean heavily upon the administration’s actions that strengthen NATO to avoid confronting the president’s rhetorical efforts to weaken it. But ignoring the damage Trump is doing does not negate it. And that damage is evident in a recent study conducted by Eurasia Group research fellow and Professor Mark Hannah. He found that Republican voters are now willing to shirk America’s responsibility to its allies. When asked if America should “initiate a military operation in Estonia to expel Russian troops” in the event of an invasion, a “slight majority” of Republicans said “no.”

Most respondents—54 percent of all voters, including two-thirds of Democrats—still believe America must come to the defense of its allies. Those who support American commitments abroad defer to formerly uncontroversial and axiomatic ideals. They say that American treaty obligations are inviolable and abandoning them would sacrifice U.S. credibility. What’s more, the failure to contain Russian military expansionism would only invite more aggression. But those who reject these notions insist that the price of defending U.S. allies in Europe from Moscow would outweigh the benefits, that NATO places unfair burdens on America, that Russia is not a threat to the U.S. homeland, and that we could risk catastrophic nuclear war if we were to impose proportionate costs on Russia for its militaristic revanchism.

This kind of craven myopia is unbecoming of Americans, much less of a party which still reveres such stalwarts as Ronald Reagan and Margaret Thatcher. Even in the abstract, Republicans of the post-War variety should be expected to understand the fundamental assumptions at the heart of deterrence theory—namely, that the ambitions of expansionist powers must be aggressively checked if only to prevent the prospect of a wider war down the road.

The specific hypothetical Hannah chose—a Russian armed incursion into Estonia—is, however, especially illuminating. Trump and his nouveau isolationist boosters on the right are fond of insisting that their animus toward NATO is rooted only in justified antipathy toward those alliance members that fail to meet their defense spending obligations. But Estonia is not among those derelict European powers. This Baltic state on NATO’s frontier has routinely met the alliance’s defense-spending requirement and has only increased its defense expenditures in the Trump era. Tallinn isn’t committing an ever-increasing pool of tax revenues to defense just because the American president is agitating to that effect. It’s bolstering its defenses because the threat from Russia has become increasingly acute.

The tensions between Russia and Estonia entered a new phase in 2007 when an effort to remove a Red Army statute from Tallinn prompted Moscow to respond with what can only be described as undeclared asymmetric warfare. Russian media broadcast false reports into Estonia claiming the statue and nearby Soviet war graves were being destroyed, yielding two nights of intense rioting and looting. A wave of cyber-attacks followed, shutting down Internet traffic, closing banks, and crippling media and government services.

A much more conventional Russian attack occurred in 2014. Then, Russian soldiers executed an assault on an Estonian border position. Russian troops deployed smoke grenades and jammed radio and telephone signals as they streamed across a customs checkpoint, capturing an Estonian counter-intelligence official and spiriting him back across the Russian border. He was subsequently convicted of espionage and sentenced to 15 years in prison but was later released in exchange for an Estonian policeman who was convicted of working for Russian security services.

Moscow continues to claim that Estonian leadership regularly evince “Russophobic rhetoric,” which prevents Russia from ratifying a mutually-agreed border treaty.

Moscow’s military incursions into former Soviet Republics like Ukraine and Georgia should be a wake-up call. Russia’s territorial ambitions are clear, and Moscow’s violations of Estonian sovereignty suggest that the Kremlin is testing its parameters. Would the Atlantic Alliance risk nuclear war to defend Tallinn’s independence? It’s hardly a foregone conclusion. Russia’s long-term strategic objective is to shatter European cohesion and break the West’s political and military alliance with Washington. Nothing would accomplish that faster than if Estonia invoked NATO’s mutual defense provisions and the cavalry did not come.

The Democratic Party’s newfound hostility toward a revisionist Russia, while welcome, is untested and may be the ephemeral product of partisan opposition to Trump’s pro-Putin rhetoric. The Democrats’ s political elites and opinion-makers remain as suspicious as ever of American military might and an extroverted foreign policy. For over a half-century, the GOP has been the natural home of Americans who instinctively understand that global peace is maintained through the projection of strength. If that’s changing, it’s an unambiguous change for the worse.