Rex Tillerson. Kevin Lamarque/Reuters In 1947, at the dawn of the Cold War, Michigan Sen. Arthur Vandenberg, a Republican, justified his firm support for the foreign policy priorities of Democratic President Harry Truman by insisting that “we must stop partisan politics at the water’s edge.”

Coming from Vandenberg, these words carried great significance, for he had spent much of his tenure in the U.S. Senate as a leading light among Republican isolationists. The Second World War and the rising Soviet threat changed Vandenberg irrevocably, and convinced him that Republicans and Democrats had no choice but to stand together in solidarity against Soviet imperialism.

One wonders what Vandenberg would make of today’s headlines. There is good reason to believe that the Russian government took extraordinary measures to tilt the scales in an American presidential election. While Democrats are furious, President-elect Donald Trump and many of his Republican allies have downplayed the news, suggesting that senior Democratic officials were to blame for leaving themselves vulnerable to Russian hacking. This isn’t partisan politics stopping at the water’s edge: It’s a hostile foreign government successfully interjecting itself in America’s partisan politics.

It’s against this backdrop that Rex Tillerson, Donald Trump’s nominee for secretary of state and until recently the chairman and CEO of Exxon Mobil Corp., faced vigorous questioning from the Senate Foreign Relations Committee on Wednesday. There is no question that Tillerson is an intelligent, articulate, and accomplished man. His years at Exxon Mobil have given him a deep understanding of the international scene. Tillerson even looks the part, something that reportedly matters an awful lot to the president-elect. It is just as easy to imagine the silver-haired Tillerson serving as secretary of state in the 1910s as it is to imagine him serving in that role in the 2010s. What makes his nomination new and interesting is that, if confirmed, he will be charged with representing America’s national interests at a time when there’s no consensus about what those interests might be.

Almost 20 years ago, political scientist Samuel P. Huntington, best known in his later years for his controversial argument that the world was heading for a “clash of civilizations,” published an essay in Foreign Affairs on “The Erosion of American National Interests.” In it, he contrasted the national unity that defined the Cold War with the division and confusion that followed, and he predicted that we were about to enter an even more divided era with lasting consequences for the projection of American power.

In Vandenberg’s day, the Republican and Democratic parties were big-tent ideological coalitions that included liberal and conservative factions. Like-minded internationalists in both parties were able to reach a consensus on various foreign policy priorities. Anti-interventionists in both parties, meanwhile, found themselves marginalized.

Obama and John Boehner. AP

To Huntington, this unity of purpose had deep cultural and ideological roots. Mid-century America was an unusually cohesive period in American history, at least among whites. In The Great Exception, liberal historian Jefferson Cowie describes how limits on immigration created a more unified, and more conformist, American culture, which helped set the stage for the New Deal consensus. The conservative author Yuval Levin makes a similar case in The Fractured Republic. Once the borders had closed, the children and grandchildren of European immigrants—including Catholics and Jews—embraced, with varying degrees of ambivalence, core tenets of Anglo-American Protestant culture. The cultural dominance of Anglo-American Protestantism gave rise to the ideological dominance of the American Creed, defined at the time by a shared commitment to liberal democracy and free enterprise. Yet this creedal consensus did not exist in a vacuum. “From the start,” Huntington observed, “Americans have constructed their creedal identity in contrast to an undesirable ‘other.’ ” Britain was the first enemy against which Americans defined themselves, but it was far from the last.

Huntington’s fear was that as America grew more culturally diverse, the creedal consensus he saw rooted in Anglo-American Protestantism wouldn’t last. And without the creedal consensus, there would be an increasing need for an outside enemy to foster national unity. Yet rising diversity would undermine our capacity for sustaining an ideological consensus, which in turn would make it far harder to choose a common enemy. Provocatively, Huntington suggested that just as WASPs in mid-century America were favorably disposed towards an alliance with Britain, members of rising immigrant groups would balance their loyalty to the U.S. against conflicting loyalties to their ancestral homelands. He anticipated a future in which the United States would grow ever less capable of influencing political outcomes in other nations in a coherent, unified fashion. Instead, the U.S. would grow vulnerable to foreign powers that would seek to exploit its internal divisions, warning that the country has “become less of an actor and more of an arena.”

Not everyone will share Huntington’s concerns about the decline of the assimilationist ethic and the rise of multiculturalism. But his vision of a more divided America lines up neatly with a number of economic developments that have transpired since his essay was published in 1997. Over the past two decades, the global division of labor has enriched educated Americans living in highly educated metropolitan areas while doing relatively little to better the lives of Americans living in less-educated small cities and rural areas. Whereas the American economy of Vandenberg’s era represented roughly half of global GDP, and opening America’s markets to international trade meant almost nothing to the nation’s dominant industries, today’s American economy no longer bestrides the world like a colossus. We might be less vulnerable to international shocks than other countries by virtue of our still-considerable size. But we’re hardly immune.

How can such a divided country unite in naming an enemy? The 9/11 terror attacks offered Americans a brief rallying point: We could all agree that al-Qaida meant us harm. But the never-ending war on terrorism has raised more questions about American identity than it’s answered. There are also those who see China as a unifying foe, a possibility that Huntington saw coming in his essay. But for every American living in a region devastated by Chinese import competition, there is another living in a place where local industries complement Chinese labor or where Chinese homebuyers contribute to soaring real estate values. Under these conditions, achieving consensus around who is and is not our enemy is inevitably elusive. The only enemies Americans can agree on these days are the Islamic State and North Korea, two entities that are about as close to mustache-twirling comic book villains as you can get.

Mitt Romney. Drew Angerer/Getty Images

So what about Russia? As recently as 2012, Mitt Romney, then the Republican presidential nominee, warned that it was America’s “No. 1 geopolitical foe,” a claim that was widely mocked and dismissed at the time, not least by his Democratic opponents. In hindsight, there is something almost quaint about Romney’s efforts to convince Americans that they had much to fear from Russia. His argument rested on the premise that we had a shared national interest that Russia threatened and that this shared national interest outweighed the potential benefits that individual Americans—or for that matter particular regions or business enterprises—might realize in a world where the U.S. accommodated the Russians.

In the end, drawing attention to Russian expansionism did Romney little good. To many Americans, the threat posed by Vladimir Putin seemed trivial when compared to the one posed by Romney himself to Obamacare, Roe v. Wade, and other domestic priorities championed by Democrats. Fast-forward to 2016, and Republican grandees like Romney failed to convince GOP primary voters that Donald Trump’s warm words for Putin were something to fret about.

One often gets the impression that Americans are warier of their domestic enemies than they are of foreign ones. This is not the first time America’s internal divisions have threatened to cripple U.S. foreign policy. During the Napoleonic era, Federalists and Republicans were divided over whether Britain or France posed the gravest threat to the fledgling republic. Similar divisions plagued the country in the run-up to the Civil War. Suffice it to say, neither period was a happy one.

Which leads us back to Rex Tillerson. As the head of Exxon Mobil, he did what was by all accounts a stellar job of representing the company’s interests, not least by currying favor with Putin. One can respect that forging relationships with unsavory governments was just part of the job. Tillerson’s new job will be much harder. If he is indeed confirmed as secretary of state, he’ll have to figure out what it means to represent America’s interests in an age when Americans are at each other’s throats, and our president-elect seems to trust Julian Assange more than the CIA. I don’t envy him.