The Washington Post’s David Ignatius highlights the questions that still remain surrounding former national security adviser Michael Flynn's resignation. (Video: Adriana Usero/The Washington Post)

It's a Watergate-era cliche that the coverup is always worse than the crime. In the Mike Flynn affair, we have the first recorded instance of a coverup in the absence of a crime.

Being covered up were the Dec. 29 phone calls between Flynn and the Russian ambassador to Washington. The presumed violation was Flynn negotiating with a foreign adversary while the Obama administration was still in office and, even worse, discussing with Sergey Kislyak the sanctions then being imposed on Russia (for meddling in the 2016 elections).

What's wrong with that? It is risible to invoke the Logan Act, passed during the John Adams administration, under which not a single American has been prosecuted in the intervening 218 years. It prohibits private citizens from negotiating with foreign powers. Flynn was hardly a private citizen. As Donald Trump's publicly designated incoming national security adviser, it was perfectly reasonable for him to be talking to foreign actors in preparation for assuming office within a month.

Flynn is gone, but a mystery remains

Worst case: He was telling Kislyak that the Trump administration might lift sanctions and therefore, comrade, no need for a spiral of retaliations. How different is this from Barack Obama telling Russian President Dmitry Medvedev, on an inadvertently open mic, during his 2012 reelection campaign, "This is my last election. After my election, I have more flexibility."

Flynn would have been giving the Russians useful information that might well have contributed to Russia’s decision not to retaliate. I’m no Russophile. But again: What’s wrong with that? Turns out, the Trump administration has not lifted those sanctions. It’s all a tempest in an empty teapot.

The accusations of misbehavior by Flynn carry a subliminal echo of a long-standing charge against Richard Nixon that he interfered in the Paris peace talks in October 1968 to prevent his Democratic opponent from claiming a major foreign policy success on the eve of the presidential election.

But that kind of alleged diplomatic freelancing would have prolonged a war in which Americans were dying daily. The Flynn conversation was nothing remotely of the sort. Where’s the harm?

The harm was not the calls but Flynn's lying about them. And most especially lying to the vice president, who then went out and told the world Flynn had never discussed sanctions. You can't leave your vice president undercut and exposed. Flynn had to go.

Up to this point, the story makes sense. Except for one thing: Why the coverup if there is no crime? Why lie about talking about sanctions? It's inexplicable. Did Flynn want to head off lines of inquiry about other contacts with Russians that might not have been so innocent? Massive new leaks suggest numerous contacts during the campaign between Trump associates and Russian officials, some of whom were intelligence agents. Up till now, however, reports the New York Times, there is "no evidence" of any Trump campaign collusion or cooperation with Russian hacking and other interference in the U.S. elections.

Thus far. Which is why there will be investigations. Speculation ranges from the wildly malevolent to the rather loopily innocent.

At one end of the spectrum is the scenario wherein these campaign officials — including perhaps Flynn, perhaps even Trump — are compromised because of tainted business or political activities known to the Russians, to whom they are now captive. A fevered conspiracy in my view, but there are non-certifiable people who consider it possible.

Trump doesn’t seem to understand the rules about making rules

At the benign end of the spectrum is that the easily flattered Trump imagines himself the great dealmaker who overnight becomes a great statesman by charming Vladimir Putin into a Nixon-to-China grand bargain — we jointly call off the new Cold War, join forces to destroy the Islamic State and reach a new accommodation for Europe that relieves us of some of the burden of parasitic allies.

To me, the idea is nuts, a narcissistic fantasy grounded in neither strategy nor history. But that doesn't mean Trump might not imagine it — after all, he maintains that if we had only stayed in Iraq to steal its oil, we wouldn't have the Islamic State. And if this has indeed been his thinking about Russia, it would make sense to surround himself with advisers who had extensive dealings there.

I believe neither of these scenarios but I’m hard put to come up with alternatives. The puzzle remains. Why did Flynn lie? Until we answer that, the case of the coverup in search of a crime remains unsolved.

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Read more on this topic:

David Ignatius: Michael Flynn’s star burns out

The Post’s View: The nation needs answers, not deflections, on Russia and Trump

Dana Milbank: Why do smart people in the White House do stupid things? Because Trump tells them to.

Paul Waldman: The Republican Congress cannot be trusted to investigate the Russia scandal

Charles Krauthammer: Trump’s foreign policy revolution