CNN's Brian Stelter: "The tiptoeing is over. The whispers are turning into shouts. President Trump's fitness for office is now the top story in the country. That's partly due to Trump's behavior... partly due to Wolff's book... partly due to Trump's reaction to the book."

ICYMI: Trump chimed in on the subject over the weekend, branding himself "a very stable genius."

P.S. N.Y. Times front-pager, "Countries See Executive Disorder in Trump's Foreign Policy Tweets":

• "Two things stand out about the foreign policy messages Mr. Trump has posted on Twitter since taking office: How far they veer from the traditional ways American presidents express themselves, let alone handle diplomacy."
• "And how rarely Mr. Trump has followed through on his words. Indeed, nearly a year after he entered the White House, the rest of the world is trying to figure out whether Mr. Trump is more mouth than fist, more paper tiger than the real thing."