In the wake of President Trump’s performance Monday in Helsinki, “treason” reigned as the No. 1 looked-up word at Merriam-Webster.

A reason, perhaps, was that the t-word was being deployed by such notables as Pulitzer Prize-winning author and New York Times columnist Thomas L. Friedman, who wrote of the “overwhelming evidence” that the president is “engaged in treasonous behavior,” and by former CIA director and ardent Trump critic John Brennan, who tweeted that Trump’s “news conference performance” was “nothing short of treasonous.”

The New York Daily News made the leap from “treasonous” to “treason” plain and simple, with a front page that quickly went viral:

And Rep. Adam Smith (D-Wash.), ranking minority-party member of the House Armed Services Committee, in his own statement, declared that “it is hard to see President Trump siding with Vladimir Putin over our own intelligence community and criminal investigators as anything other than treason.”

In an interview with the Seattle Times, Smith backed away slightly, saying his use of the word “treason might have been a little bit of hyperbole.”

That was a wise rhetorical de-escalation, as University of Texas law professor Steve Vladeck made clear in a tweet:

Perhaps some who used the term were speaking more broadly, using Merriam-Webster’s second definition, “the betrayal of a trust.”

But nothing Trump did in Helsinki and nothing he has done otherwise that anyone knows of are likely to qualify as treason, at least by its legal definition.

“Treason against the United States,” says Section 3, Article III, of the U.S. Constitution, “shall consist only in levying war against them, or in adhering to their enemies, giving them aid and comfort.” It’s the only crime explicitly defined in the nation’s founding charter. The framers clearly wanted it used sparingly, declaring that “no person shall be convicted of treason unless on the testimony of two witnesses to the same overt act, or on confession in open court.” The absence of an “overt act,” among other factors, helped former vice president Aaron Burr win an acquittal in 1807 in the most famous treason trial of all, after he was accused of plotting to set up his own empire in the west.     

Trump and treason? “No, not at all,” Carlton F.W. Larson, an expert on the subject at the UC Davis School of Law, told The Washington Post.

“It’s funny,” he said, “because people keep asking me if it’s treason yet. He could hand the nuclear codes over to Putin and it wouldn’t be treason. This isn’t anything as bad as that. Groveling in front of a foreign leader, putting the interests of a foreign country ahead of the United States, displaying horrific judgment in foreign policy — none of those things are treason.”

Trump would have to be participating in waging war against the United States or giving “aid and comfort” to the nation’s enemies to be vulnerable to treason charges, either in a court or an impeachment proceeding.

Problem one: The United States is not at war.

Under the treason law, Larson said, “levying war is a situation where people who owe allegiance to the United States are gathering in force, usually to overthrow the government, to shut down the government or make it inoperable in some kind of way.

“There you would need Trump actually being part of that. If you thought that the hacking rose to the level of war — that’s a hard sell. By analogy, suppose Trump had sent burglars over to the DNC to rifle through their files. Nobody would say that’s treason. That’s Watergate.”

“Hacking into a private organization to steal its documents seems most analogous to a burglary,” Larson wrote in an essay on the Take Care blog. “Likewise, hacking into a voting machine to change the results seems most analogous to ballot stuffing or ballot tampering. A crime has clearly been committed, but not the crime of treason.”

Problem two: There must be an enemy to aid and comfort.

While many may think of Russia as an adversary and even an enemy, it has not been declared so. An “enemy,” Harvard Law School professor Laurence Tribe said in an email to The Post, “arguably” requires a formal state of war.

“Some commentators,” Tribe writes with co-author Joshua Matz in “To End a Presidency: The Power of Impeachment,” “have argued that Russia also ranks among our ‘enemies’ ” because of its hacking to influence the 2016 election in Trump’s favor. The argument is “interesting and important,” they write, but “continued legal uncertainty about whether it is treasonous to lend ‘aid and comfort’ to Russia militates against basing an impeachment on this theory.” There are plenty of other potential crimes in the Russia investigation, they write, but probably not treason.

Larson agreed. “I think that a cyberattack that is designed to cripple the U.S. government, that looks a lot like a traditional act of war,” he said. But there has been no such attack, and the United States has not been treating cyberattacks as war. And if it did, “China is notorious for that, right. They’re constantly probing and messing around with our computer systems. But I don’t think we’re at a state of war with China.”

As Larson noted in a law review article, even during the Cold War, the “Soviet Union was never an ‘enemy’ of the United States under the Treason Clause because it was never at open war with the United States. Accordingly, persons who allegedly spied for the Soviet Union, such as Julius and Ethel Rosenberg, were convicted of espionage, not treason.”

None of this has stopped Trump himself from throwing around the t-word. Democrats criticize him, he said in February, “even on positive news. . . . Somebody said ‘treasonous.’ I mean, yeah, I guess, why not? Shall we call that treason? Why not?”

After Helsinki, what enraged Smith and made Friedman “sick to my stomach” was, among other things, Trump’s failure to do anything about Russia’s behavior and his siding with Russia over the U.S. intelligence and law enforcement communities.

“Trump is simply insanely obsessed with what happened in the last election,” Friedman wrote. “But now he is president, and the fact that he may not have colluded with the Russians doesn’t mean he does not, as president, have a responsibility to ensure that the Russians be punished for interfering in our last election on their own and be effectively deterred from doing so in the future. That is in his job description.”

In his column, he defined “treasonous behavior” as “behavior that violates his oath of office to ‘preserve, protect and defend the Constitution of the United States.’ ” That would be heinous, but not treason.

“At every turn of his trip to Europe,” Smith said in his statement, “President Trump has followed a script that parallels Moscow’s plan to weaken and divide America’s allies and partners and undermine democratic values. There is an extensive factual record suggesting that President Trump’s campaign and the Russians conspired to influence our election for President Trump. Now Trump is trying to cover it up. There is no sugar coating this. It is hard to see President Trump siding with Vladimir Putin over our own intelligence community and our criminal investigators as anything other than treason.”

Conspiracy to, say, obstruct justice is a crime, but not the crime of treason.

“My guess,” Larson said, “is that these people are using the term sort of in a looser rhetorical sense,” to mean, perhaps, something like definition 2, betrayal.