It was a straightforward question, posed to the country’s leading authority on infectious diseases, Anthony S. Fauci, at a White House briefing on Sunday. What did Fauci think about the use of the anti-malarial drug hydroxychloroquine? What medical evidence existed to demonstrate that it was an effective treatment against covid-19, the disease caused by the coronavirus that has swept across the world this year?

Before Fauci could answer, he was interrupted by President Trump, standing just to his right.

“Can I have a chance to answer that question?” Trump said to Fauci, who acquiesced.

Trump dismissed the question outright, despite the likelihood that Fauci would have said, as he has in the past, that he is withholding judgment until controlled trials are complete.

“He’s answered that question 15 times,” Trump insisted. Fauci offered a slight smile, by now used to sharing a podium with the president.

In recent weeks, Trump’s focus on advocating unproven medical treatments for the virus — and fervently defending that advocacy — has emerged as one of the most perplexing aspects of the White House’s response to the coronavirus pandemic. Why is Trump so dedicated to promoting the use of hydroxychloroquine — and not just to authorize its use but to repeatedly, actively, vocally hype it? What’s the rationale behind the president identifying particular drugs which have not been proven to be effective and making them a central part of his messaging at a critical time?

Speculation about Trump’s motivation usually quickly runs toward economics. Does the president have some stake in companies that produce the medicines? There’s no evidence that he does; he sold his individual stocks upon taking office. Besides, the way stocks are faring at the moment, a strategy based on making a buck on moving the markets seems risky.

The answer is probably instead rooted in who Trump is and how he operates as president. Promoting a theory that runs against the recommendations of experts is a hallmark of Trump’s approach to politics since even before his entry into the 2016 presidential race. Then, once Trump decided that this was a fight he wanted to have, his allies swung into action cobbling together a scaffolding of theories to offer support. Hydroxychloroquine is, by now, a part of the political culture wars, as surely as is climate change — and because of similar logic about the value of expertise.

There’s not much downside for Trump. If he’s wrong, he moves on. But if he’s right that the drug is effective? He wins twice over: proof that the experts are no match for his instinct and building out his rhetoric about how effective his response to the pandemic has been.

The idea that this and other drugs were particularly effective in the fight against covid-19 popped up on social media in the middle of last month and migrated onto Fox Business and Fox News. The first mention of hydroxychloroquine by name as a treatment appears to have been on March 16 by Marc Siegel, a doctor who serves as a contributor to the networks. Hours later, an attorney named Gregory Rigano appeared on Laura Ingraham’s prime-time show, where he claimed that the drug could get rid of the coronavirus “completely.” Two days later, Fauci himself appeared on Ingraham’s show, where the host asked him about the treatments. Fauci recommended caution.

Trump began promoting hydroxychloroquine and azithromycin shortly afterward, hyping them as potentially being “one of the biggest game changers in the history of medicine.” Fox News host Sean Hannity began regularly touting the medications in his nightly programming. In one three-day period last month, the liberal watchdog group Media Matters tallied 109 mentions of hydroxychloroquine and the related medication chloroquine on Fox News alone.

It’s an established feature of Trump’s presidency that he often equates advice from random associates with the information he gets from government experts. So the well-defined Fox-to-Trump-to-Fox feedback loop has been supplemented by ancillary figures who promote Trump’s message, including back to himself.

Celebrity doctor Mehmet Oz has appeared repeatedly on Fox News to discuss the medications, with Trump reportedly recommending to aides that he wanted Oz’s input. Former New York mayor Rudolph W. Giuliani — a figure central to the events that led to Trump’s impeachment last year — has been promoting the drugs, as The Post reported on Sunday.

Giuliani has hyped them more than a dozen times in the past few weeks and has on a few occasions reportedly done so to Trump directly. Politico reported last week that Trump has also been influenced by Oracle CEO Larry Ellison, a major campaign donor, who offered to set up a database tracking use of the medication.

Inside the White House, Trump’s position has been advocated by loyal allies. Adviser Peter Navarro reportedly got into a heated argument with Fauci in the White House on Saturday after Navarro insisted that the drugs at issue had demonstrated “clear therapeutic efficacy.” Fauci recommended caution, given that the efficacy has not been shown in controlled trials. What was presented as evidence was simply anecdotal, he said, frustrating Navarro.

On Monday morning, Navarro appeared on “Fox & Friends,” Fox News’s morning program. Asked about the debate over the drugs — which the show has promoted repeatedly — Navarro defended his and the president’s position.

“I think history will judge who's right on this debate, but I'd bet on President Trump's intuition on this one,” he said, “because of all the doctors I've talked to and all the scientific papers I've read, and they're about this high."

Those are the anecdotal reports to which Fauci was referring. But Navarro’s presentation here is revealing: It’s Trump’s intuition against medical expertise — and he’s banking on the former.

So does Trump. While touring the Centers for Disease Control and Prevention last month, he insisted that he had a knack for medical science, based in part on having had an uncle who taught at MIT for “like, a record number of years."

“I like this stuff. I really get it,” Trump said. “People are surprised that I understand it. Every one of these doctors said, ‘How do you know so much about this?’ Maybe I have a natural ability. Maybe I should have done that instead of running for president.”

During the same visit, he told reporters that he wanted to leave passengers on a cruise ship docked near San Francisco so that any who might be infected would not be added to the country’s total number of infections.

Trump on Sunday likened his advocacy of the medications to his support for “right to try” legislation, which streamlined the ability of patients to use experimental medications for serious illnesses. That legislation is something he regularly mentions as one of his keys accomplishments as president.

If clinical trials do show that the drugs are particularly effective, it’s easy to predict how Trump would respond. He has repeatedly insisted that he effectively tamped down the number of deaths from the virus because in January he advocated for curtailing travel from China, where the virus emerged. That travel ban was loose, allowing tens of thousands of people to arrive in the United States, but it has become a central part of Trump’s defense of his administration’s response to the pandemic. If he could also claim that he was right about these medications, one can assume that would become integral to his rhetoric.

“What do you have to lose?” Trump said on Sunday about the use of the medications. “And a lot of people are saying that when — and are taking it, if you’re a doctor, a nurse, a first responder, a medical person going into hospitals, they say taking it before the fact is good. But what do you have to lose? They say take it. I’m not looking at it one way or the other. But we want to get out at this.”

The country has stockpiled 29 million doses of the medication, he said at another point. He touted the Food and Drug Administration’s “rapid approval” of use of the medication, implying that it was approved for treatment of coronavirus, which it wasn’t.

“So if it does work, it would be a shame if we didn't do it early,” he added. “But we have some very good signs."

Trump has repeatedly couched his recommendations by noting that he’s not a doctor. He will also often add “maybe not”-style asterisks to his advocacy of the drugs, as he did on Sunday when he was asked why he was promoting them.

After saying he wasn't promoting the drugs, he continued.

“It's a very special thing. Now, it may not work, in which case, hey, it didn't work. And it may work, in which case it's going to save a lot of lives,” Trump said. “Now a lot of people say if the people walking in prior to getting it, if they take it, it has a profound effect. Well, maybe it does and maybe it doesn't.”

Former FDA commissioner Scott Gottlieb, who served for the first two years of Trump’s administration, made an important point about the efficacy of the drugs on Sunday. They are already being used — but the pandemic is still raging.

“Doctors have been using it widely in U.S., often in combo with azithromycin, since very outset,” Gottlieb wrote on Twitter. “They used it based on a theoretical potential for benefit, the fact that it was widely available, and a perception that side effect profile is understood so risk/reward favorable. Anyone who believes it needs to be 'made available' should be assured that it is available, and has been widely used for months all around the world. If the drug combo is working its effect is probably subtle enough that only rigorous and large scale trials will tease it out."

The president’s focus on the medications is not without cost, despite his “what do you have to lose” framing. The administration’s focus on stockpiling the medication has made them less readily available for people who need them for their intended treatments, including those who have lupus. An elderly couple in Arizona who had seen reports about using chloroquine to treat coronavirus ingested a related chemical, killing one and hospitalizing the other.

What’s more, the Politico report last week indicated that administration officials were being diverted from other efforts in order to work on proving Trump’s hunch correct.

“The White House directed health officials to set up a project to track if the antimalarial drugs chloroquine and hydroxychloroquine show promise — a dayslong effort that distracted from urgent tasks like trials of other medicines thought to have more potential against the virus,” Sarah Owermohle and Dan Diamond reported. “Food and Drug Administration officials also reversed a nearly six-year ban on a troubled Indian manufacturer in a bid to secure the drugs, and top advisers to Trump have encouraged other agencies to locate as much of the product as possible."

What's particularly remarkable about Trump's embrace of the unproven medications is how they were accompanied over the weekend by his dismissal of obvious, proven measures for containing the virus.

Asked on Saturday if he would wear a face mask to help prevent transmission of the coronavirus, Trump said he wouldn't.

“I think that wearing a face mask as I greet presidents, prime ministers, dictators, kings, queens — I don’t know, somehow I don’t see it for myself,” he said. “I just don’t. Maybe I’ll change my mind."

By Sunday, he hadn’t. Trump was asked if he had been encouraged by first lady Melania Trump to wear a mask, given her advocacy of them on social media.

“Again, I would wear one if it was — if I thought it was important,” Trump replied.

After Trump interrupted Fauci's answer about the use of hydroxychloroquine, another reporter asked the doctor why he wasn't wearing a mask.

“There are a couple of reasons,” Fauci said. “One of them is that part of the — in fact, the major reason to wear a face mask is to protect you from infecting [others]. I had my test yesterday, and it’s negative."

“That’s a very — very good answer,” Trump interjected. “All right. I think that really could be it. That was a — I love that answer. Especially on the face mask. I thought it was very good."

The briefing moved on.