It is hard to exaggerate the potential significance of the news, first reported by CNN, that the president's former lawyer, Michael Cohen, can testify that Donald Trump both knew in advance and approved of the June 9, 2016, meeting at Trump Tower between his campaign's high command and Kremlin emissaries who promised dirt on Hillary Clinton. There was already substantial evidence that the Russian intervention helped to make Trump president and that individuals associated with the Trump election effort, from campaign chairman Paul Manafort on down, had dealings with the Russians. What has been missing is proof that the president was personally involved in these sordid machinations.

There was already circumstantial evidence suggesting Trump knew of the Russian offer to demonstrate "support for Mr. Trump." Before and after the 2016 meeting, Donald Trump Jr. called a blocked number three times. His father's private number was blocked, but prosecutors should be able to subpoena the phone records. And, on June 7, 2016, hours after the meeting was scheduled, candidate Trump announced: "I am going to give a major speech on probably Monday of next week and we're going to be discussing all of the things that have taken place with the Clintons. I think you're going to find it very informative and very, very interesting." The Russians' promise of dirt apparently did not pan out, and the speech was never given, but there is good cause to suspect the Russians simply decided it would be more effective to give their dirt (i.e., stolen emails) to WikiLeaks rather than handing it directly to the Trump campaign.

What has been lacking so far is the "smoking gun." Cohen may just supply it, if his purported testimony is credible and corroborated (big ifs). Rudy Giuliani, Trump's lawyer, has gone from arguing that Trump didn't know about the Trump Tower meeting to arguing that the then-candidate wasn't present (no one has alleged he was) and from arguing that no collusion occurred to arguing that collusion, even if it occurred, is no big deal. This is his actual defense: "My client didn't do it, and even if he did it, it's not a crime."

Giuliani's comments echo other Trump loyalists. Former New Jersey governor Chris Christie: "Collusion is not a crime." Fox host Tucker Carlson: "It's hard to see the point of all this hysteria. What exactly would the crime be here? It's not illegal to talk to foreigners. Nobody's claiming any information changed hands, but even if it did, so what?" Mollie Hemingway of the Federalist, in a tweet that was liked by Trump Jr.: "I don't have a problem w/getting dirt on election opponents from foreigners."

We are very, very close to the Putin Republicans arguing that they're glad he worked with the Kremlin to beat "Crooked Hillary." In fact, some MAGA-heads have already made this very case. It is, after all, the natural culmination of the hysteria of so many Trumpists. If you believe, as former White House aide Michael Anton argued, that the Democrats are the moral equivalent of the al-Qaeda terrorists who hijacked Flight 93, then anything is permissible to save the country. Even collusion with its enemies.

Reality check: It is not OK for the president and his minions to work with a foreign power to influence a U.S. election. It is shocking that this argument even has to be made. If the allegations of collusion are true, then the Trump campaign conspired with the Russians to violate numerous statutes. As laid out by law professor Ryan Goodman during Senate testimony, these include "conspiracy to defraud the United States" by interfering with the lawful functioning of federal elections; anti-hacking laws that prohibit unauthorized access to computers and transmission of information gained thereby; and campaign-finance rules that prohibit candidates from soliciting or receiving anything of value from foreign nationals. Above all, there is obstruction of justice: If Trump knew about the offer of Russian help, that greatly strengthened his motive to fire FBI Director James Comey to stop the inquiry into the "Russia thing."

But we should not get lost in legalities, because the likelihood is that special counsel Robert Mueller won't try to indict a sitting president. The proper remedy is impeachment, and "high crimes and misdemeanors" can be whatever Congress says they are. While it's true that "collusion" isn't a federal crime, it is a crime in the court of public opinion. Imagine how loudly Trump and his partisans would scream if Mexico were to secretly work with Democrats to stop him from being reelected. The crime is potentially even more serious in Trump's case because Mexico is an ally while Russia is an enemy. If Republicans would regard it as "treasonous" for Democrats to collude with Mexico, how can they avoid the conclusion that the president has betrayed America if he colluded with Russia?

That is a rhetorical question. The pathetic truth is that Republicans now think if Trump does it — whatever "it" is — it's not a crime.

Max Boot is a columnist for The Washington Post.

What's your view?

Got an opinion about this issue? Send a letter to the editor, and you just might get published.