Donald Trump was proclaiming his low opinion of the American intelligence services even before the election. But when they said that Russian hacking had helped elect him, his tweeting on the subject took on the feel of sweaty-palmed panic.

On New Year’s Eve, he tried so hard that he blurted out the childish final argument for which there’s never a response: “I also know things that other people don’t know.”

Well, sure he does; he’s the president-elect, privy to special briefings. He needn’t beat his chest about it. All presidents have known things other people don’t know. But what is it, exactly, that he knows about the Russian hacking? He said we’d know on Tuesday or Wednesday. Would that be like his promised press conference about conflict of interest? He cancelled that one and we forgot about it.

I can’t help but wonder if what he knows is something he desperately hopes will not be made public, that the intelligence reports will provide concrete evidence of Russian aid in his election, undermining his legitimacy as president.

Here’s why I wonder. His comment called to mind a remark a Russian official in Moscow made during the campaign, saying that Moscow was in regular contact with Mr. Trump’s campaign. It got little attention at the time, and no reporter I know tried to follow up that lead.

So the question becomes what does Trump know and when did he know it? That was the searing question Sen. Howard Baker, the Tennessee Republican, asked about Richard Nixon during the Watergate hearings. The answer damned Nixon’s presidency.

Trump’s effort to undermine the credibility of the intelligence reports began to get feverish right after President Obama expelled 35 Russian diplomats in direct retaliation for meddling in the American election. He immediately repeated a tweet from the day before that it was “time to move on to bigger and better things” and that he would listen to a briefing about it on Tuesday. On Tuesday he tweeted that the briefing had been put off until Friday implying that the briefers “needed more time to build a case,” adding “Very strange,” encouraging more suspicion.

The Washington Post quoted a government official as saying that the briefing had not been delayed, that Trump received a briefing on Tuesday, perhaps was unsatisfied by it, and would receive another on Friday. The Post said Friday’s briefing would be based on the larger inquiry into the hacking that President Obama had ordered and that briefers were obligated to brief the president on it before briefing Trump. Meanwhile Trump cozied up to Julian Assange of WikiLeaks suggesting that Assange was more reliable than American intelligence. It became a concerted effort to discredit in advance whatever the official report said.

This is not normal and in a president-elect it is unacceptable, indeed treasonous to undermine the public’s trust in government security and intelligence in a time of foreign aggression, whether by cyber attack or otherwise. President Putin has made it clear he wanted Trump to become president, and Trump made it clear he considered Putin a better president than Barack Obama. Giving aid and comfort to the enemy is treason.

Donald Trump may be the only president in American history to have become impeachable before taking office.