President Trump speaks with Russian Foreign Minister Sergei Lavrov, left, and Russian Ambassador to the U.S. Sergei Kislyak during a meeting at the White House in Washington on May 10. (Russian Foreign Ministry via Agence France-Presse)

Jacob Heilbrunn is the editor of the National Interest.

Tucker Carlson’s Fox News show subsists on controversy, which usually consists of the host administering a verbal thrashing to that evening’s liberal guest. But things took an unexpected turn last night when Carlson and the military analyst Ralph Peters, a Fox stalwart, began denouncing each other over Russia policy:

Perhaps nothing better illustrates the topsy-turvy world of GOP foreign policy, in which hard-bitten realists are increasingly squaring off against more idealistic neocons, than their riveting standoff. The issue is fundamental: Should the Trump administration work with autocrats or go for regime change? Should we empathize with the predicaments of our adversaries or seek to take them out?

Carlson, who has emerged as a champion of President Trump, regularly defends his emollient approach to Russia and its president, Vladimir Putin. As Carlson rehearsed the argument that it’s imperative for Americans to make common cause with Putin in fighting the Islamic State in Syria, Peters replied: “He is malevolent and he is as close to pure evil as I can find. He’s also brilliant. I don’t understand what any American would want an alliance with Russia. We should be strengthening our alliance with democracies instead of trashing NATO — we should be building it up much more strongly.”

After Carlson suggested that the United States has worked with bad actors in the past — as it happens, one such was Joseph Stalin in World War II — and that there was no cogent reason not to reach out and snuggle up to Putin, Peters went for the jugular. “You sound like Charles Lindbergh in 1938 saying ‘Hitler hasn’t attacked us,’ ” Peters said. Instead of crumpling, as Peters clearly thought he would, Carlson fired back. “You cannot compare me to someone who made apologies for Hitler. And I don’t think Putin is comparable to Hitler.” For good measure, Carlson went on to paste Peters for his championing of the Iraq War in 2003, noting that he would hate to dredge up his columns from back then — which, incidentally, amounted to a form of doing just that.

For all Carlson’s indignation, it’s hardly surprising that Peters would invoke Lindbergh and the isolationist GOP. World War II is the great test case that conservative realists in both America and Great Britain flunked. Realists like to claim that the internal character of a regime is inconsequential and that all states react the same way to external stimuli, as though they were billiard balls devoid of morality or even impetuosity. Sir Nevile Henderson, an arch-appeaser and ambassador to Berlin, said at the time, “One must also try to understand the German point of view. If we were in Germany’s place what would we … be doing: exactly what I think the Germans are today doing.”

Indeed, when it came to Hitler himself, American conservative realists were quite forgiving. The Wall Street Journal editorial page, in June 1940, when Hitler’s tanks were rolling through France, called for “realism” in foreign policy and said that the Fuhrer had “already determined the broad lines of our national life for at least another generation.” By December 1941, it became clear that the isolationist America First movement had actually left America last.

But if World War II, “their finest hour” and Churchillian chest-thumping has become the neocon template for all conflicts, it is also one that has led to grief in Iraq and elsewhere. Fear of a new Munich can serve as a blank check for intervention anywhere and everywhere, leading to catastrophes such as Iraq, which Carlson and Trump have both been quick to invoke. Before the Iraq War in 2003, realists warned about the dangers of hubris in invading Iraq, pointing to the inauspicious prospects for successfully implanting a functioning democracy in the arid sands of the Middle East. Ever since the Iraq War went south, it is the realists who have increasingly had the rhetorical upper hand in debates about intervention abroad.

Whether Trump himself is a consistent, let alone conscious, realist, however, may be doubted. One week he is bombing Syria and avowing his fealty to Article 5. The next he is talking about cozying up to Putin and forming a joint cybersecurity unit. One day he calls North Korean leader Kim Jong Un a “pretty smart cookie.” Another he breathes fire about North Korea’s intercontinental ballistic missile testing. And so on.

Still, his championing of “America first,” his apparent inclination to let bygones be bygones when it comes to Russian meddling in the 2016 election, his enthusiasm for Saudi Arabia, his indifference to human rights – writing in Foreign Policy, Suzanne Nossell complained that Trump “isn’t even moved by the courage of the powerless citizen who challenges the strongman; between authoritarian rulers and the dissidents who challenge them, he chooses the former almost every time” — and his avidity to work with repressive leaders indicate that Trump, on the most basic level, is on board with some crude version of realism. Trump, you could even say, is trying to take the GOP back to the future.

This is why the melee between Peters and Carlson wasn’t a sideshow, but a sign that the fight over foreign policy in the GOP isn’t going away. Maybe it’s just getting started.