Presidential historian Jon Meacham said that if President Donald Trump knew about Russian efforts to interfere in the 2016 election, that could match “the definition of treason.”

“Is it is possible that our ordinary political vocabulary, our ordinary vernacular, really isn’t commensurate with what’s happening here,” Meacham said on Morning Joe Tuesday. “If, in fact — and it’s a subjunctive — Donald Trump knew about the Russian efforts on his behalf, then there’s a live question about whether he has been giving aide and comfort to the enemy, which is the definition of treason in the Constitution.”

“So this just isn’t who wins the week, who loses the week conversation. This is an existential constitutional crisis because it’s quite possible that the President of the United States right now is a witting or at least partially witting agent of a foreign power,” Meacham continued.

Meacham also compared the current legal turmoil engulfing Trump to Richard Nixon‘s downfall.

“It was a very rapid cascading effect in ’73,” he said. “So the break in is June 17th, ’72. Nixon doesn’t resign until August 8th, ’74. The hearings began, I think it was May of ’73. But this was the season, the last quarter of ’73 when Nixon said ‘I’m not a crook’, which would have fit on Twitter.”

Meacham added that the economy is important to watch: “I believe that he’s been propped up artificially of what I think of 401(k) Trump supporters. Because their numbers were up they were willing to give him a pass on the rest of it.”

Watch above, via MSNBC. H/t Contemptor.

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