Getty / The Atlantic

If Donald Trump defies the odds and wins a second term, the next four years will likely be more disruptive to U.S. foreign policy and world affairs than the past four have been. Think of his reelection as a pincer movement, an attack on the international order from two sides. Trump will consolidate his control over the institutions of government, bending them to his will, removing any lingering resistance from the Republican Party. Meanwhile, by confirming that the United States has rejected its traditional leadership role, a second Trump term would make a lasting impact on the world right when it is at a particularly vulnerable moment. U.S. alliances would likely crumble, the global economy would close, and democracy and human rights would be in rapid retreat.

Trump’s first term has had a clear narrative arc. He systematically purges his government of those who stand up to him and replaces them with loyalists who indulge his whims and worldview. If he is still president on January 21, Trump will feel utterly vindicated by a second unlikely victory—thinking that only he is truly in touch with the American people.

In a second term, Trump will insist on loyalty with every appointment, but two types of loyalists exist. The first is senior Republicans who are steadfastly loyal even if they personally disagree with Trump on certain issues, such as Russia or military intervention in the Middle East. These figures are cut from the mold of Mike Pompeo. They include Senators Tom Cotton and Lindsey Graham, former United Nations Ambassador Nikki Haley, and Secretary of the Treasury Steve Mnuchin. Trump may give these people senior positions, but they will not be free to contradict the president or to pursue their own agendas unless they temporarily align with Trump.

The second group is the ultra-loyalists, who owe their positions entirely to Trump’s patronage. These are political operatives such as Richard Grenell, who was Trump’s ambassador to Germany and acted as director of national intelligence for 96 days, and retired military officers and now–cable-news commentators such as Anthony Tata and Douglas McGregor. This group also includes the ultra-ultras—Trump’s family members, who have played a role in his first term, and could be given formal positions of authority in a second. Think of Jared Kushner as national security adviser or secretary of state if Republicans retain a majority in the Senate.

With a loyal team in place, what does Trump want to do? The most optimistic theory is that he will be a responsible nationalist. With no elections left to fight and with a conviction that he set the world straight in his first term, he will let things be. For instance, he will be happy with NATO because member countries have committed to paying more for their own defense. His administration’s key policy driver will be to transform U.S. strategy for an era of great-power competition, particularly against China.

The responsible-nationalist theory has very little evidence to support it, though. Trump has never personally endorsed the key argument of his National Security Strategy, about great-power competition—not even in his December 2017 remarks introducing the plan. He is currently very hawkish on China, but that is possibly because he sees his rhetoric as a way to deflect attention from his failures on the coronavirus. He is still more motivated by narrow trade and economic concerns than by broader geopolitical interests in the Indo-Pacific. This theory also leaves out Trump and highlights policy documents that he played little role in creating.

The most accurate guide to Trump’s behavior has never been his views on a particular issue. It has always been his psychological profile and disposition—his paranoia, how he sees himself, his desperate need to be at the center of the news cycle, his susceptibility to flattery, his fury at perceived slights, and his deeply seated visceral instincts. Mary Trump’s family history provides more insights into Donald Trump’s plans than official documents do.

Given who the president is, another theory—Trump unbound—seems more likely. In this scenario, his appetite will grow with the eating. As John Bolton concludes in his book, Trump in a second term will be “far less constrained by politics than he was in a first term.” He will be free to be himself—to pursue policies that benefit him personally by linking decisions to his business interests; by indulging his desire for ratings and drama; and by attacking people he does not like, such as Angela Merkel, and helping people he does, such as Kim Jong Un.

Substantively, he will double down on his instincts, leaning into ideas he had before he became president. He could pull the plug on NATO entirely by refusing to defend Germany, France, and other selected countries under the mutual-defense clause. He could make this decision unilaterally, without authorization from Congress, as it simply entails altering a presidential interpretation of the purposefully vague NATO founding treaty.

He’s already tried to withdraw troops from South Korea in his first term. But he could make it happen in his second by entering into a peace treaty with North Korea. His first comments on foreign policy in the 1980s were criticisms of Japan, but earlier in his first term he modified his long-standing hostility because of his friendship with Shinzo Abe, which the then–prime minister carefully cultivated. Now, with Abe out of the picture, Trump could revert to Japan-bashing and questioning the alliance with Japan itself. Both of these steps could weaken U.S. competitiveness with China.

China is the big unknown in a second Trump term. The Republican foreign-policy establishment hopes that rivalry with China will be the organizing principle of U.S. foreign policy. If Trump buys into that stance, then these officials might use that to make the case for their preferred positions toward the Middle East (stay engaged to keep China out), on Europe (get NATO on board against China), and on economics (trade with your friends to compete with China). But no one knows whether Trump will support this agenda or whether he will pivot back to a much narrower form of competition with Beijing, one focused solely on economics while pulling back from America’s alliances.

The second part of the pincer movement—how the rest of the world will react—is also important in a second term. America’s allies and adversaries took a deep breath after the 2016 election. They did not know if Trump’s win was a temporary blip or a permanent change—indeed, this is the top question most foreign governments have had about the United States over the past four years, because it is so consequential to their future. Before the coronavirus hit, most allied foreign officials I spoke with tentatively thought that Trump would win a second term. Now, like almost everyone else, they see him as the underdog. If he wins again, friend and foe alike will accept that the post–World War II period of American leadership has come to a definitive end. The effect will vary from country to country. Some allies may cut deals with China and Russia. A small number could seek an independent nuclear deterrent. All will prepare for a world with less cooperation.

The coronavirus makes matters much worse. Many now widely accept that ordinary life will not return until a reliable vaccine is developed and widely distributed. The global economy is still teetering on the brink, rocked by the virus and the rivalry between the United States and China. Cooperation, particularly between the U.S. and Europe, has ground to a halt. The Trump administration’s priority is to signal its “America First” bona fides to its base rather than to build an international coalition to tackle shared problems. In a second Trump term, foreign countries can expect no coordination on the global economic recovery, the development of a vaccine, the repair of international institutions, or aid for those that were destabilized by the crisis. Openness—in terms of travel and trade—will not return to what passed for normal before the coronavirus. Every nation will have to fend for itself. The European Union and a handful of other democracies may try to keep the multilateral order alive, but it will become a relic, largely irrelevant to world events.

Autocrats—Vladimir Putin, Xi Jinping, Mohammed bin Salman, Recep Tayyip Erdoğan, and others—have been both deeply insecure and emboldened during Trump’s first term. They see him as a kindred spirit and are confident in their ability to influence and persuade him. Trump acknowledged as much to Bob Woodward: “It’s funny, the relationships I have—the tougher and meaner they are, the better I get along with them … The easy ones are the ones I maybe don’t like as much or don’t get along with so much.” Those cozy relationships will continue and accelerate in a second term. Trump is easy to read, and with a mixture of flattery and inducements, the leaders will enlist Trump in their own causes, whether the elimination of dissent at home or turning a blind eye to regional aggression.

Looking back on U.S. diplomatic history, one of the great counterfactuals is what would have happened if Franklin D. Roosevelt had not replaced his vice president Henry Wallace with Harry Truman in 1944. Wallace was sympathetic to the Soviet Union and became an ardent opponent of the Cold War. If he had become president when FDR died, in April 1945, the next half century could have gone very differently—likely no NATO, no Marshall Plan, no alliance with Japan, no overseas troop presence, and no European Union.

The U.S. is now teetering on another historically important moment. With Trump, we would not only be deprived of our Truman. We would be saddled with our Wallace—a leader whose instincts and actions are diametrically opposed to what the moment requires. With few remaining constraints and a vulnerable world, a reelected Trump could set the trajectory of world affairs for decades to come.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.