President Donald Trump is using a new false talking point on the campaign trail to downplay the effectiveness of face masks in fighting the coronavirus pandemic. He likely adopted it after seeing a similar falsehood deployed on Tucker Carlson Tonight, one of his favorite Fox News programs. The situation presents a case study in how the president has leaned on the network’s right-wing commentators to shape the federal response to the pandemic, with deadly results.

On Thursday, Trump repeatedly mangled a study to falsely suggest that face coverings may not prevent -- and may actually promote -- the spread of the virus. 

“They come out with things today — did you see, the CDC? That 85% of the people wearing the masks catch it, OK?” he said during a rally in Greenville, North Carolina. 

He repeated the claim during a prime-time town hall event on NBC. “Just the other day,” he said, “they came out with a statement that 85% of the people that wear masks catch it.” 

“They didn't say that,” moderator Savannah Guthrie responded. “I know that study. That's not --”

“Well, that's what I heard,” Trump replied, “and that's what I saw.”

When Trump later attempted to return to the figure, Guthrie said, “I looked at that report. It's not about mask wearing — it was neutral on the question of masks.”

More than 10 million Americans watched the president’s dubious critique of masks.

But Guthrie is correct about the study, which was published in September by the Centers for Disease Control and Prevention and did not focus on mask use. Based on a survey of 314 people from 11 health care facilities, it focused on the impact of going to public places where masks cannot easily be worn, such as restaurants with on-site eating and bars. The study concluded that “adults with positive SARS-CoV-2 test results were approximately twice as likely to have reported dining at a restaurant than were those with negative SARS-CoV-2 test results.” It also found that close contact with someone who also tested positive was a major risk factor. 

“It’s misleading to leap to conclusions about the effectiveness of masks from the CDC report, since most participants reported wearing them and the study was not controlling for mask use,” PolitiFact pointed out after reviewing it and speaking to experts. 

But Trump is likely telling the truth that he “heard” and “saw” something different, because the Trump-Fox feedback loop is powering his talking point. On Tuesday and Wednesday, one of his favorite Fox hosts, Tucker Carlson, promoted a misinterpretation of the study that had bubbled up from right-wing blogs. Trump is misinterpreting Carlson's misinterpretation.

“Almost everyone — 85 percent — who got the coronavirus in July was wearing a mask, and they were infected anyway,” Carlson said during his Tuesday monologue. Carlson and his guest, Alex Berenson, who regularly uses Fox’s platform to suggest masks are ineffective, painted that result as scientific evidence that the media are hiding from the public out of a misguided effort to talk up masks.

Carlson and others in right-wing media were leaning on the survey findings that of the 154 people who reported testing positive, 70.6% said they “always” wear a mask and 14.4% said they “often” did. But their conclusion is not a correct interpretation of the data, according to the CDC and experts PolitiFact consulted.

Carlson has at times acknowledged that “masks work” and that “dozens of research papers have proved it.” But the Fox host has also downplayed their effectiveness while relentlessly seeking to turn their use into a culture war flashpoint, and this is not the first study he has misinterpreted to do so. His commentary is part of an ongoing anti-mask campaign by key Fox personalities with influence over the president.

That coverage is reflected in Trump’s unwillingness to champion mask use, even as his CDC director, Dr. Robert Redfield, calls them “one of the most powerful weapons we have to slow and stop the spread of the virus.” Fox commentators are the president’s closest advisers, and in responding to the coronavirus he has relied on prime-time hosts like Carlson, not public health experts like Redfield.

Fox founder Rupert Murdoch is reportedly “disgusted” by Trump’s handling of the virus, scorning his unwillingness to listen to experts. But Trump is listening to Murdoch’s employees instead. Trump is downplaying the effectiveness of masks because Carlson is telling him they aren’t effective, and Carlson is in that position because Rupert and his son, Lachlan, want him there. 

The upside is that Carlson made a lot of money and gets great ratings for the Murdochs’ network. The downside is that a lot of Americans are dead because the president takes advice from him and his colleagues.