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To understand the corruption, chaos, and general insanity that is continuing to engulf the Trump campaign and much of the Republican Party right now, it helps to understand the predicate embraced by many Trump supporters: If Joseph R. Biden Jr. wins the presidency, America dies.

During last week’s Republican National Convention, speaker after speaker insisted that life under a Biden presidency would be dystopian. Charlie Kirk, the young Trump acolyte who opened the proceedings, declared, “I am here tonight to tell you—to warn you—that this election is a decision between preserving America as we know it and eliminating everything that we love.” President Trump, who closed the proceedings, said, “Your vote will decide whether we protect law-abiding Americans or whether we give free rein to violent anarchists and agitators and criminals who threaten our citizens. And this election will decide whether we will defend the American way of life or allow a radical movement to completely dismantle and destroy it.” And in between Americans were told that Democrats want to “disarm you, empty the prisons, lock you in your home, and invite MS-13 to live next door” and that they “want to destroy this country and everything that we have fought for and hold dear.”

“They’re not satisfied with spreading the chaos and violence into our communities. They want to abolish the suburbs altogether,” a St. Louis couple who had brandished weapons against demonstrators outside their home, told viewers. “Make no mistake, no matter where you live, your family will not be safe in the radical Democrats’ America.”

One does not have to be a champion of the Democratic Party to know this chthonic portrait is absurd. But it is also essential, because it allows Trump and his followers to tolerate and justify pretty much anything in order to win. And “anything” turns out to be quite a lot.

In just the past two weeks, the president has praised supporters of the right-wing conspiracy theory QAnon, which contends, as The Guardian recently summarized it, that “a cabal of Satan-worshipping Democrats, Hollywood celebrities and billionaires runs the world while engaging in pedophilia, human trafficking and the harvesting of a supposedly life-extending chemical from the blood of abused children.” Trump touted a conspiracy theory that the national death toll from COVID-19 is about 9,000, a fraction of the official figure of nearly 185,000; promoted a program on the One America News Network accusing demonstrators of secretly plotting Trump’s downfall; encouraged his own supporters to commit voter fraud; and claimed Biden is controlled by “people that are in the dark shadows” who are wearing “dark uniforms.”

Trump believes his own government is conspiring to delay a COVID-19 vaccine until after the election. He retweeted a message from the actor James Woods saying New York Governor Andrew Cuomo “should be in jail” and another from an account accusing the Portland, Oregon, mayor of “committing war crimes.” The president is “inciting violence,” in the words of Maryland’s Republican Governor, Larry Hogan. Trump defended 17-year-old Kyle Rittenhouse, a supporter who is charged with first-degree homicide; and stated that if he loses the election in November it would be because it was “rigged.” At the same time, the second-ranking House Republican, among other of the president’s supporters, has shared several manipulated videos in an effort to damage Biden.

This is just the latest installment in a four-year record of shame, indecency, incompetence, and malfeasance. And yet, for tens of millions of Trump’s supporters, none of it matters. None of it even breaks through. At this point, it appears, Donald Trump really could shoot someone on Fifth Avenue and not lose his voters.

This phenomenon has no shortage of explanations, but perhaps the most convincing is the terror the president’s backers feel. Time and again, I’ve had conversations with Trump supporters who believe the president is all that stands between them and cultural revolution. Trump and his advisers know it, which is why the through line of the RNC was portraying Joe Biden as a Jacobin.

Republicans chose that theme despite the fact that during his almost 50 years in politics, Biden hasn’t left any discernible ideological imprint on either the nation or his own party. Indeed, Biden is notable for his success over the course of his political career in forging alliances with many Republicans. I worked at the Office of National Drug Control Policy in the early 1990s when William Bennett was its director and George H. W. Bush was president. Biden was then chair of the Senate Judiciary Committee; he and his staff were supportive of our work, and not in the least ideological. There will be no remaking of the calendar if Joe Biden becomes president.

Still, in the minds of Trump’s supporters lingers the belief that a Biden presidency would usher in a reign of terror. Many of them simply have to believe that. Justifying their fealty to a man who is so obviously a moral wreck requires them to turn Joe Biden and the Democratic Party into an existential threat. The narrative is set; the actual identity of the nominee is almost incidental.

A powerful tribal identity bonds the president to his supporters. As Amy Chua, the author of Political Tribes: Group Instinct and the Fate of Nations, has argued, the tribal instinct is not just to belong, but also to exclude and to attack. “When groups feel threatened,” Chua writes, “they retreat into tribalism. They close ranks and become more insular, more defensive, more punitive, more us-versus-them.”

That works both ways. Fear strengthens tribalistic instincts, and tribalistic instincts amplify fear. Nothing bonds a group more tightly than a common enemy that is perceived as a mortal threat. In the presence of such an enemy, members of tribal groups look outward rather than inward, at others and never at themselves or their own kind.

The danger of this mindset—in which the means, however unethical, justify the ends of survival—is obvious. And so in this case, Trump supporters will tolerate everything he does, from making hush-money payments to porn stars and engaging in sexually predatory behavior, to inviting America’s adversaries to intervene in our elections, to pressuring American allies to dig up dirt on the president’s opponent, to cozying up to some of the worst dictators in the world, to peddling crazed conspiracy theories, to mishandling a pandemic at the cost of untold lives, to countless other ethical and governing transgressions. Trump is given carte blanche by his supporters because they perceive him as their protector, transforming his ruthlessness from a vice into a virtue.

In my experience, if Trump supporters are asked to turn their gaze away from their perceived opponents, and instead to focus and reflect on him and on his failures, they respond in a couple of consistent ways. Many shift the topic immediately back to Democrats, because offering a vigorous moral defense of Donald Trump isn’t an easy task. It’s like asking people to stare directly into the sun; they might do it for an instant, but then they look away. But if you do succeed in keeping the topic on Trump, they often twist themselves into knots in order to defend him, and in some cases they simply deny reality.

“Motivation conditions cognition,” Jonathan Rauch, a senior fellow at the Brookings Institution and a contributing writer at The Atlantic, wisely told me. Very few Trump supporters I know are able to offer an honest appraisal of the man. To do so creates too much cognitive dissonance.

That they are defending a person who is fundamentally malicious, even if he makes judicial appointments of which they approve, is too painful for them to admit. They are similarly unable to admit they are defending an ethic that is at odds with what they have long championed. They have accepted, excused, and applauded Trump’s behavior and tactics, allowing his ends to justify his means. In important respects, this is antithetical to a virtue ethic. So once again, it’s easier for them to look away or engage in self-deception; to convince themselves that Donald Trump is not who he so clearly is.

These reactions aren’t confined to Trump supporters; people across the political spectrum struggle with confirmation bias and motivated reasoning, in giving too much benefit of the doubt to those with whom we agree and judging too harshly and unfairly those with whom we disagree. That is part of the human condition. The degree to which Democrats, including feminists, overlooked or accepted Bill Clinton’s sexually predatory behavior—including his campaign’s effort to smear his accusers and its use of a private investigator to destroy Gennifer Flowers’s reputation “beyond all recognition”—is an illustration of this. So Flowers was branded a “bimbo” and a “pathological liar,” even though Clinton later, under oath, admitted to having an affair with her.

"If you drag a $100 bill through a trailer park, you never know what you'll find,” James Carville said in response to Paula Jones’s claim that Clinton sexually harassed her. In defending President Clinton against the charges of sexual harassment made by Kathleen Willey, who accused Clinton of groping her without her consent, Gloria Steinem wrote, “The truth is that even if the allegations are true, the President is not guilty of sexual harassment. He is accused of having made a gross, dumb and reckless pass at a supporter during a low point in her life. She pushed him away, she said, and it never happened again. In other words, President Clinton took ‘no’ for an answer.” And Nina Burleigh, who covered the White House for Time magazine, said, “I’d be happy to give him a blowjob just to thank him for keeping abortion legal. I think American women should be lining up with their presidential kneepads on to show their gratitude for keeping the theocracy off our backs.” So Democrats should be careful about looking down at others for accommodating themselves to unsavory and even repulsive characters for the sake of partisanship.

But what’s different in this case is that Trump, because of the corruption that seems to pervade every area of his life and his damaged psychological and emotional state, has shown us just how much people will accept in their leaders as a result of “negative partisanship,” the force that binds parties together less in common purpose than in opposition to a shared opponent. As the conservative writer David French has put it, with Donald Trump and his supporters we are seeing “negative partisanship in its near-pure form, and it’s the best way to explain Trump’s current appeal to the Republican party.” His ideology is almost entirely beside the point, according to French: “His identity matters more, and his identity is clear—the Republican champion against the hated Democratic foe.”

I know plenty of Trump supporters, and I know many of them to be people of integrity in important areas of their lives. Indeed, some are friends I cherish. But if there is a line Donald Trump could cross that would forfeit the loyalty of his core supporters—including, and in some respects especially, white evangelical Christians—I can’t imagine what it would be. And that is a rather depressing thing to admit.

Polarization and political tribalism are not new to America; fear and hatred for our fellow citizens have been increasing for decades. We’ve had plenty of presidents who have failed us, in ways large and small. But this moment is different because Donald Trump is different, and because Donald Trump is president. His relentless assault on truth and the institutions of democracy—his provocations and abuse of power, his psychological instability and his emotional volatility, his delusions and his incompetence—are unlike anything we’ve seen before. He needs to be stopped. And his supporters can’t say, as they did in 2016, that they just didn’t know. Now we know. It’s not too late—it’s never too late—to do the right thing.

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