The journalists call Trump the country's "first seditious president" in a new foreward to their 1974 book "All the President's Men."
Bernstein's remark, made on CNN's Reliable Sources on Sunday, appeared to shock host Brian Stelter.
The venerated newsman recently railed against media "enablers" for the spread of misinformation about COVID-19.
The Watergate journalist said Trump "is putting his own narrow presidential re-election efforts in front of the safety, health and well-being of the people of the United States."
The co-author of All the President's Men told CNN that Mitch McConnell had a strategy to "wear out his own members" to stop a vote for more witnesses.
"We don't know. Senators are very sensitive to the will of the people and if the people in this country turn on these facts and this president, I think the Senate might as well," Carl Bernstein said in an interview with CNN Tuesday.
"We've never had a president of the United States who mortgaged our foreign policy interests," Watergate journalist Carl Bernstein added.
"Mueller has enormous power here to move the perception of Americans," Carl Bernstein said.
The veteran journalist said the situation challenged "whether our institutions are able to function in this country to deal with a president of the United States who is unique in our history, who has nothing but contempt for Democratic traditions and the rule of law."
"And that is the great danger because everything he does plays to this base that is his way of staying in office, if he can stay in office and be re-elected."
"This is about the most serious counterintelligence people we have in the U.S. government saying, 'Oh, my God, the president's words and actions lead us to conclude that somehow he has become a witting, unwitting, or half-witting pawn," Carl Bernstein said.
GOP members are saying that Trump "is unfit on psychological grounds, that he is unfit perhaps because of his contempt for the law," Carl Bernstein claimed.
"We have a president who does not believe in truth," Carl Bernstein said. "This is far different from anything we have experienced."
"Comical to watch @CNN covering for leftist hack @carlbernstein," Trump Jr. tweeted.
"So many lives have been ruined over nothing—McCarthyism at its WORST!"
"Jared Kushner has many, many strikes lining up against him in the Mueller investigation," Carl Bernstein said.
The 1974 book tells the story of the Watergate scandal, and some readers are finding it newly relevant.
Watergate journalist Carl Bernstein says the president's attacks on the media are 'more treacherous than Richard Nixon's attacks on the press.'