Veteran journalist Carl Bernstein bemoaned the difficulty of separating possible criminal behavior by President Trump from what is "merely outrageous and vile."

During a panel Friday on the season finale of Bill Maher's HBO show "Real Time," Maher noted how he believes "crimes are happening in the present," providing examples of Trump recently calling former intelligence heads "political hacks," while cozying up to foreign rivals like Russian President Vladimir Putin and China's Xi Jinping during his trip to Asia this month.

"Part of the problem ... is how do you separate what might be criminal, what might be a conspiracy, from the merely outrageous and vile," Bernstein replied. "And it's very difficult to do in this presidency with a abhorrent president."

Bernstein, best known for his investigative reporting that shed light on the Watergate scandal leading to former President Richard Nixon's resignation in 1974, then applauded the press for coaxing out both kinds of stories. He also repeated his past statements about how Republican and military leaders say in private that Trump is not fit to be president.

Maher also asked if Trump was guilty of "public collusion" in how he appears protective of Putin over the Russian president's claim that he did not meddle in the 2016 election.

Bernstein rejected the suggestion that this could be impeachable behavior, but opined that Trump's "embrace of Putin without any thought given to the actions of Putin to undermine our elections in this country is extreme."

He added that this is also a reason that Robert Mueller was appointed special counsel to look into Russian interference and whether the Trump campaign colluded with Russia.

Bernstein said he isn't sure where that investigation will go, but did stress that he believes there is a some sort of Trump-centric cover-up.

"What we do know is there's a cover-up going on and the president does not want us to know what the cover-up is about," he said. "Whether it's indeed about something that happened with enabling the Russians or it has to do with his family money. What we know is he sought to demean, undermine, obstruct, not necessarily obstruction of justice, obstruct these investigations to keep us from knowing what this is really about."