President Trump posted a photo of himself wearing a face mask on Monday and tweeted that "many people say that it is Patriotic to wear a face mask when you can’t socially distance."

Why it matters: It's the first time Trump has ever tweeted a picture of himself in a mask, which he had not worn in public until he visited Walter Reed National Military Medical Center earlier this month. The president appeared to mock his opponent Joe Biden for wearing a mask in public in May.

What he's tweeting: "We are United in our effort to defeat the Invisible China Virus, and many people say that it is Patriotic to wear a face mask when you can’t socially distance. There is nobody more Patriotic than me, your favorite President!"

The big picture: After months of a partisan debate over wearing masks, two-thirds of Americans — and a noticeably increasing number of Republicans — now say they’re wearing a face mask whenever they leave the house, according to the Axios-Ipsos Coronavirus Index.

• Scientific evidence shows face masks can help to control the spread of the coronavirus, but the nuances and changes in messaging about their use have complicated public health efforts.
• The changing tide comes as coronavirus infections surge across much of the country, threatening to overwhelm hospital systems in Republican-led states like Florida, Arizona and Texas.