Trump shared a tweet mocking Biden for wearing a face mask in public — in line with the CDC advice that the president routinely ignores

• President Donald Trump on Monday shared a tweet mocking his presumptive 2020 Democratic presidential challenger, Joe Biden, for wearing a face mask at a public Memorial Day appearance.
• "This might help explain why Trump doesn't like to wear a mask in public," said the tweet from Brit Hume, a Fox News commentator, next to a picture of Biden wearing a black mask.
• Biden's decision to wear a masks contrasts with Trump's refusal to wear one in public.
• The Centers for Disease Control and Prevention recommends that people cover their face in public settings where social distancing is not practical. The idea is that masks could help keep people with coronavirus infections from spreading the virus when they speak.

President Donald Trump on Monday shared a tweet mocking his presumptive 2020 Democratic presidential challenger, Joe Biden, for wearing a face mask during a public appearance for Memorial Day.

"This might help explain why Trump doesn't like to wear a mask in public. Biden today," said the message by Brit Hume, a Fox News political commentator, alongside a message of Biden wearing a black mask and sunglasses.

Biden wore the mask when he appeared in public for the first time in more than two months to lay a wreath at a military memorial in Delaware.

His decision contrasted with Trump's refusal to wear a mask in public, at times in defiance of local rules.

In response to the gibe, Biden's defenders were quick to point out that Biden was acting in accordance with advice from state authorities.

The state of Delaware has urged people to "wear face coverings in public settings" to try to slow the spread of the novel coronavirus.

The Centers for Disease Control and Prevention advises "wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies)." Masks are thought to help stop people with coronavirus infections from spreading the virus by trapping at least some of the viral particles when they speak.

Trump's refusal to wear a mask in recent public appearances has drawn criticism.

On a visit to a Ford plant in Michigan last week, Trump wore a mask for part of the trip but took it off in front of the cameras. Michigan Attorney General Dana Nessel accused the president of acting like a "petulant child" for flouting the measure.

The president said he had been "given a choice" about wearing a face covering.

"I had one on in an area where they preferred it, so I put it on and it was very nice. But they said, 'Not necessary here,'" Trump told reporters.

He gave the same reason for not wearing a mask on a factory tour in Arizona earlier in May.

But even though the White House itself introduced a rule requiring visitors and staff members to wear masks, Trump has in several briefings been the only top official not wearing one.

According to recent reports, Trump believes wearing a mask in public makes him look unpresidential and could damage his image on the campaign trail. He has argued publicly that he is tested often for the virus and is therefore confident he is not at risk of spreading it.

Biden, in contrast, has urged Americans to "follow the science" and told ABC News in April that he would wear a mask in public.