Carl Bernstein says the Trump administration could put the United States in a "more dangerous" situation than the Watergate scandal did during President Richard Nixon's tenure.

Bernstein, a CNN contributor whose reporting for the Washington Post helped topple Nixon in the 1970s, said Sunday on CNN's "Reliable Sources" that he is concerned Republicans in Congress haven't voiced more skepticism of President Trump's decision to fire FBI Director James Comey last week.

Comey's department was investigating potential ties between the Trump campaign and Russia.

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"The Republicans during Watergate were heroic. They are the ones who said, 'What did the president know, and when did he know it?'" Bernstein said.

He added that those Republicans investigated and supported the impeachment of Nixon "because they were willing to see the truth served." Nixon resigned before a trial in the U.S. Senate could happen.

Bernstein said there has not been "something similar" yet from Republicans today. He said while "numerous" members of the party have been quietly critical of Trump, conservative leadership has been either silent or supportive of him.

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"It's a different dynamic than we've ever had to deal with before," he said. "Richard Nixon was a criminal president. Donald Trump is a president with whom there is grave question about his fitness and ability to conduct the office of the president -- and that's going hand-in-hand with the possible coverup into collusion with a foreign power."

Bernstein said he thinks it's more difficult for journalists to work today than during the Nixon era. Fewer people are interested in the "best obtainable version of the truth," he said.

Instead, he said they look for information on both sides to support what they already believe.