"We're in foreign territory," Bernstein said, speaking on CNN's "New Day." "We have never been in a malignant presidency like this before. It calls on our leaders, it calls on our journalists to do a different kind of reporting, a different kind of dealing with this presidency and the President."
Bernstein went on to argue that the Trump presidency's deepest problems are becoming an open secret in Washington.
"I think something much greater is happening, and that is that we are in the midst of a malignant presidency," he said. "That malignancy is known to the military leaders of the country. It's known to the Republican leadership in Congress who recognize it, and it's known to the intelligence community."
"That has got our leaders worried," he continued. "They are worried about his character. They are worried about his capabilities. They are worried about his temperament and state of his temperament, to use kind words here."
Bernstein, a CNN contributor whose reporting on the Watergate scandal for The Washington Post led to the resignation of President Richard Nixon in 1974, added: "[R]eporters need to go out and talk to [those leaders] either off the record, on background, about the question of their confidence in this President and whether or not he is capable of being the President of the United States in a way that defends us, our country, and the Constitution of the United States. Many members of Congress, many of our military leaders, many in our intelligence community who I've spoken to, and I know other reporters have spoken to, understand and are beginning to comprehend that the underlying story here is a lack of confidence in the abilities and character of the President of the United States of America."
"This President is not in control of the presidency in a way that it is functioning, and that has got our leaders worried," Bernstein said.
"We have to ... be kind of medical reporters right now," he added. "I don't mean about the President's psyche, but rather about every aspect of his presidency, and how and whether it is functioning, because many aspects are not functioning."
His remarks come at the end of a week in which Trump has battered the media with insults, including an early morning tweet storm Thursday in which he attacked the intellect and appearance of MSNBC's "Morning Joe" co-hosts Joe Scarborough and Mika Brzezinski. Those tweets drew wide condemnation from across the political spectrum in Washington and beyond.
Bernstein's comments put the blame for what he said was dysfunction within the Trump administration on the President himself.
The Trump presidency, he said, "is not functioning partly because of his character. It's not functioning partly because of his attacks on the press, which is totally moving the needle that the American people ... are watching. ... But it's really not functioning because the character and capabilities of this President are called into grave question in a way that those who know him best are raising serious concerns about."