The official line from the White House, as with other matters surrounding the president’s physical health and appearance, is that Mr. Trump’s glow is the result of “good genes,” according to a senior administration official who would speak only on the condition of anonymity.

And, O.K., a little powder — a translucent one, not a bronzer — which the president applies himself before television appearances, the official said.

But mysteries abound. One persistent question: Does Mr. Trump use a tanning bed, as a talkative makeup artist said in 2016 and Omarosa Manigault Newman, a former aide, claimed in a tell-all book? (Ms. Manigault Newman wrote that an usher was fired for mishandling transport of the contraption.)