Watergate investigation legend Carl Bernstein called on Congress to hold hearings to determine if President Donald Trump is fit to hold office.

“What’s really going on here is that Bob Woodward’s book, and the contents of what is in the anonymous piece in The New York Times, is that those closest to the president of the United States are saying we must save the country from the president,” Bernstein told Anderson Cooper on CNN.

“What we need here are, finally, I think, some congressional hearings in which, in executive session or open session, those around the president of the United States are questioned about the fitness of Donald Trump to be the president of the United States,” said the CNN analyst, who was Woodward’s reporting partner in uncovering the Watergate scandal of the Nixon administration.

“It is very important for the leadership in the Congress of the United States and the people of the United States to know whether or not Donald Trump is fit to be president — whether he is stable enough to be president, honest enough to be president and has the capabilities of being president. ... The people closest to him have the gravest doubts.”

Bernstein said that Trump’s behavior is “no surprise” to Republicans in Congress.

Check out what else he has to say in the video above. Bernstein begins speaking at 13:45.

Earlier on Thursday, Sen. Elizabeth Warren (D-Mass.) said senior administration officials should invoke the 25th Amendment of the Constitution to remove Trump from office. The amendment allows the vice president to take over in case the president is removed from office, dies, resigns or becomes incapacitated.

CORRECTION: A previous version of this story mischaracterized Warren’s comments on the 25th Amendment. She suggested senior administration officials should invoke it, not Congress.