President-elect Donald Trump has shocked America’s European allies yet again. In a joint interview with the Times of London and German publication Bild, he denigrated NATO as “obsolete” and added, “A lot of these countries aren’t paying what they’re supposed to be paying, which I think is very unfair to the United States.” His proviso that “NATO is very important to me” was not enough to calm nerves in Europe. “Trump’s attitudes have raised alarm bells across Europe,” The Washington Post reported after German Chancellor Angela Merkel responded to Trump’s remarks by curtly saying, “We Europeans have our destiny in our own hands.” Russia, meanwhile, welcomed Trump’s remarks. “NATO is indeed a vestige [of the past] and we agree with that,” said Dmitry Peskov, President Vladimir Putin’s spokesman.

It’s tempting to see the rift between the U.S. and its European allies as an unprecedented shift in foreign policy. After all, NATO is a venerable institution that has endured 68 years with bipartisan support. Even Trump’s pick for secretary of defense, retired General James Mattis, strenuously disagrees with him on NATO and on the wisdom of seeking friendlier ties with Russia. “I think right now,” he said during his confirmation hearing last week, “the most important thing is that we recognize the reality of what we deal with in Mr. Putin and we recognize that he is trying to break the North Atlantic alliance and we take the integrated steps—diplomatic, economic, military and the alliance steps, working with our allies—to defend ourselves where we must.”

Yet beneath that façade of bipartisan accord, there has always been a powerful strain of isolationism and unilateralism within the Republican Party. If Trump does try to revolutionize U.S. foreign policy, he won’t have to do it alone; he can summon and bolster that minority faction in his own party that has always seen NATO as both a waste of money and an unnecessary constraint on America’s freedom of action—or inaction, as the case may be—abroad.

When President Harry Truman’s push for the creation of the North Atlantic Treaty Organization in 1949, he was met with opposition by Ohio Senator Robert Taft, leader of the conservative wing of the Republican Party. A notorious penny-pincher, Taft argued that NATO would soon “cost more each year than the housing, education, and limited health plans combined,” and he presciently warned that the alliance would lead to a costly arms race. “We cannot build up the armaments of Western Europe without stimulating the Russians to increase still further their development of war forces,” Taft said. He feared that such an escalated Cold War would lead to “bankruptcy and the surrender of all liberty.”

When Taft lost the Republican nomination to Dwight Eisenhower in 1952, it seemed that this strain of unilateralism and isolationism had suffered a permanent defeat. But it didn’t die; it became a recessive gene within the GOP, revealing itself now and again. Several Republican presidents have shown a Taft-like willingness to sideline allies in pursuit of an “America First” policy, notably Richard Nixon’s unilateral decision in 1971 to delink American currency from the gold standard and to impose a 10 percent tariff on all imports, creating the famous “Nixon Shock” in Europe and Asia. In its “war on drugs,” the administration also forced allies to accept policies by fiat. When the Reagan administration took office in 1981, it inherited Nixon’s tendency to unilateral action on key issues, trying to impose its will on European allies on controversial issues like American attempts to impose an embargo on a pipeline bringing natural gas from the Soviet Union to Europe, and American support for anticommunist guerrillas in South Africa (both policies that Europeans as a whole disapproved of).