Just before midnight on March 22nd, the President of the United States prepared to tweet. Millions of Americans, in the hope of safeguarding their health and fighting the rapidly escalating spread of COVID-19, had already begun to follow the sober recommendation of Anthony S. Fauci, the country’s leading expert on infectious disease. Fauci had warned Americans to “hunker down significantly more than we as a country are doing.” Donald Trump disagreed. “WE CANNOT LET THE CURE BE WORSE THAN THE PROBLEM ITSELF,” he tweeted.

Trump had seen enough of “social distancing.” In an election year, he was watching the stock market collapse, unemployment spike, and the national mood devolve into collective anxiety. “I would love to have the country opened up, and just rarin’ to go by Easter,” he said, on Fox News. “You’ll have packed churches all over our country. I think it’ll be a beautiful time.”

Trump’s Easter forecast came more than two months after the first U.S. case of COVID-19 was identified, in Washington State, and more than a hundred days after the novel coronavirus emerged, first from bats and then from a live-animal market in the Chinese city of Wuhan. Every day, more people were falling sick and dying. Despite a catastrophic lack of testing capacity, it was clear that the virus had reached every corner of the nation. With the Easter holiday just a few weeks away, there was not a single public-health official in the United States who appeared to share the President’s rosy surmises.

Anthony Fauci certainly did not. At seventy-nine, Fauci has run the National Institute of Allergy and Infectious Diseases for thirty-six years, through six Administrations and a long procession of viral epidemics: H.I.V., SARS, avian influenza, swine flu, Zika, and Ebola among them. As a member of the Administration’s coronavirus task force, Fauci seemed to believe that the government’s actions could be directed, even if the President’s pronouncements could not. At White House briefings, it has regularly fallen to Fauci to gently amend Trump’s absurdities, half-truths, and outright lies. No, there is no evidence that the malaria drug hydroxychloroquine will provide a “miracle” treatment to stave off the infection. No, there won’t be a vaccine for at least a year. When the President insisted for many weeks on denying the government’s inability to deliver test kits for the virus, Fauci, testifying before Congress, put the matter bluntly. “That’s a failing,” he said. “Let’s admit it.”

When Trump was not dismissing the severity of the crisis, he was blaming others for it: the Chinese, the Europeans, and, as always, Barack Obama. He blamed governors who were desperate for federal help and had been reduced to fighting one another for lifesaving ventilators. In one briefing, Governor Andrew Cuomo, of New York, said, “It’s like being on eBay with fifty other states, bidding on a ventilator.” Trump even accused hospital workers in New York City of pilfering surgical masks and other vital protective equipment that they needed to stay alive. “Are they going out the back door?” Trump wondered aloud.

As a reporter who writes mainly on science and public-health issues, I’ve known Fauci since the H.I.V./AIDS epidemic exploded, in the mid-eighties. He once explained to me that he has developed a method for dealing with political leaders in times of crisis: “I go to my favorite book of philosophy, ‘The Godfather,’ and say, ‘It’s nothing personal, it’s strictly business.’ ” He continued, “You just have a job to do. Even when somebody’s acting ridiculous, you can’t chide them for it. You’ve got to deal with them. Because if you don’t deal with them, then you’re out of the picture.”

Since his days of advising Ronald Reagan and George H. W. Bush, Fauci has maintained a simple credo: “You stay completely apolitical and non-ideological, and you stick to what it is that you do. I’m a scientist and I’m a physician. And that’s it.” He learned the value of candor early. “Some wise person who used to be in the White House, in the Nixon Administration, told me a very interesting dictum to live by,” he told me in 2016, during a public conversation we had at the fifty-year reunion of his medical-school class. “He said, ‘When you go into the White House, you should be prepared that that is the last time you will ever go in. Because if you go in saying, I’m going to tell somebody something they want to hear, then you’ve shot yourself in the foot.’ Now everybody knows I’m going to tell them exactly what’s the truth.”

Americans have come to rely on Fauci’s authoritative presence. Perhaps not since the Vietnam era, when Walter Cronkite, the avuncular anchor of the “CBS Evening News,” was routinely described as the most trusted man in America, has the country depended so completely on one person to deliver a daily dose of plain talk. In one national poll, released last Thursday, seventy-eight per cent of participants approved of Fauci’s performance. Only seven per cent disapproved.

On March 23rd, Fauci failed to appear at the daily briefing in the White House pressroom. Twitter promptly lost its mind. #NoFauci became a top trending topic, followed closely by #whereisFauci and #letTonyspeak. There was speculation that Trump, who is inclined to fire anyone who disagrees with him or, worse, garners some praise in the media, had lost patience with Fauci. As one of Fauci’s old friends told me, “This is a President who doesn’t give a shit about Fauci’s accomplishments, his history, or his learning. If anything, they’re negatives.”

The truth was less alarming. “I was tied up in a task-force meeting, and we were trying to work out some difficult policies,” Fauci said. “I have no trouble with the President. When I talk to him, he listens.” My experience with Fauci suggested that this last statement was perhaps a triumph of pragmatism over accuracy. His priority, as he’s made clear, is to do what is necessary to save lives. So I was not surprised to receive an e-mail from Fauci the following day, saying that he had been asked to refrain from participating in personal profiles. It seemed that it was one thing for him to talk about the news with reporters or even to chat on Instagram with Stephen Curry, the Golden State Warriors star. But focussing on himself, rather than on the President, was another thing entirely.

Fauci and Trump are about as odd a duo as American political life has ever produced. Both men are in their seventies. Both come from the outer boroughs of New York City. Both are direct, even blunt. But that’s where the resemblance ends. Fauci has always been a person of unusual discipline. Nearing eighty, he works about eighteen hours a day. Long ago, when his three children were young, he and his wife, Christine Grady, who runs the bioethics department at the National Institutes of Health, decided to maintain the sanctity of family dinners by starting them when he got home from the office, at around nine o’clock. For decades, Fauci has taken long lunchtime runs, but, during the crisis, he’s cut back his routine to power walking––and only on weekends. Fauci parses his words with care and believes, above all, in the power of facts and the efficacy of data.

David Baltimore, a Nobel laureate and a pioneer of molecular biology, told me, “Tony is unique, in that he has such credibility with politicians that he’s been able to insert hard facts into the conversation. That has been wonderful for our country and the world.” According to David Relman, a microbiologist at Stanford University who for years has advised the government on biological threats, “Tony has essentially become the embodiment of the biomedical and public-health research enterprise in the United States. Nobody is a more tireless champion of the truth and the facts. I am not entirely sure what we would do without him.”

Fauci can be impatient with the compromises of politics. In my conversations with him, he has responded furiously when a dicey amendment, a bogus rider, or a “poison pill” is attached to a public-health bill. He recalled one congressional provision, in 2016, that tried to make it “legally permissible to fly the Confederate flag at national cemeteries. I am not kidding.” When dealing with politicians, he told me, he relies on the pseudo-Latin expression Illegitimi non carborundum: Don’t let the bastards grind you down. But he has inspired respect throughout the political world and beyond. Fauci’s office walls are covered with scores of photographs of him with Presidents, senators, visiting Prime Ministers, business leaders, actors. In October, 1988, George H. W. Bush, during a Presidential debate with Michael Dukakis, was asked who his heroes were. “I think of Dr. Fauci,” Bush replied. “You’ve probably never heard of him. . . . He’s a very fine researcher, a top doctor at the National Institutes of Health, working hard, doing something about research on this disease of AIDS.”

These days, nearly everyone has heard of Fauci. Pandemic-memorabilia entrepreneurs have put his face on bottle openers, coffee mugs, and bumper stickers: “In Dr. Fauci we trust.” The National Bobblehead Hall of Fame and Museum has produced a seven-inch likeness of him, partly to raise money to produce protective gear for medical workers. There’s a Facebook group called Dr. Fauci Speaks, We Listen, and another called Dr. Fauci Memes for Social Distance Teens. A petition has circulated to nominate him as People’s “sexiest man alive.”

On right-wing social media and talk radio, Fauci has a different image: he is routinely disparaged as a closet lefty who is exaggerating the threat of the coronavirus. “Has anyone else noticed that every suggestion by Dr. Doom Fauci just happens to also be the worst possible thing for the economy?” the conservative Internet TV host Bill Mitchell tweeted. “That’s not an accident folks.” An analysis in the Times found more than seventy Twitter accounts that have pushed the hashtag #FauciFraud, with some tweeting out anti-Fauci bile hundreds of times a day. “There seems to be a concerted effort on the part of Trump supporters to spread misinformation about the virus,” Carl Bergstrom, a professor of biology at the University of Washington who has studied misinformation, told the paper. “There is this sense that experts are untrustworthy, and have agendas that aren’t aligned with the people.” Fauci has received so many personal threats that the Justice Department recently approved a security detail for him. Fauci shrugged it off, telling reporters, “I’ve chosen this life.”

The crisis that the world now faces comes as no surprise to Fauci. On January 10, 2017, ten days before Trump took the oath of office, Fauci delivered the keynote address at a conference at Georgetown University, titled “Pandemic Preparedness for the Next Administration.” After describing his years of managing epidemics, he posed a series of questions to the audience: “Will there be a resurgence of Zika? We’re getting into the summer in South America. Are we going to see a resurgence or not? What about influenza? Are we going to get a new pandemic?”

Fauci’s last point, he emphasized, was almost certainly the most important: the possibility that some unknown, powerfully infectious pathogen could emerge to threaten the world. “What about things that we’re not even thinking about?” he said. He let the question drift out over the hall. “What is for sure,” he concluded, “is that, no matter what, history has told us definitively that it will happen.”

On the day that Anthony Stephen Fauci was born, the front-page headline in the Times was “PRESIDENT TO GIVE EMERGENCY FACTS TO NATION ON RADIO.” It was Christmas Eve, 1940. The Second World War had begun, and the United States was less than a year away from joining the fight.

Fauci grew up in southwest Brooklyn, first in Bensonhurst and later in Dyker Heights, where his family ran a pharmacy and lived in an apartment upstairs. The pharmacy was across the street from the Shrine Church of St. Bernadette. When Mass was finished on Sundays, Fauci recalled, people would walk over to get prescriptions filled and to buy whatever else they needed for the coming week. Tony’s father, Stephen, dispensed medications, and was known to customers as Doc. His mother, Eugenia, worked the register, along with his older sister, Denise. From an early age, Tony spent evenings and weekends riding around the neighborhood on his Schwinn, making deliveries.