General Michael Flynn's guilty plea for lying to the FBI about contacts with Russian ambassador Sergey Kislyak is a major step forward in an investigation that will lead to the impeachment of President Donald Trump.

Or it's not. In fact, it's a sign that Robert Mueller's investigation is running out of steam.

The rampant speculation as to what Flynn's plea means or doesn't mean in the ongoing "Russia investigation" is a perfect reflection of the tribalism that afflicts American culture and politics at the end of 2017 - a tribalism that is easy for our adversaries in the world to exploit.

Those who ardently wish to see the end of what they consider a dangerous and illegitimate presidency can hardly contain their excitement at each step - no matter how small or opaque in its significance - in an investigative process they hope will bring Trump down.

Those who defend Trump - despite his team's obvious obfuscations over Russia - insist that there's really nothing to see here, that the nature of the charges against Flynn, Paul Manafort and George Papadopoulos actually "prove that there was no collusion."

The question of collusion is itself misleading; it's being used as a kind of shorthand for possible criminal activity. But collusion itself is not a crime. It is possible that there was cooperation between the Trump campaign and Russia. It is possible that that cooperation violated specific statutes, such as election laws. We don't know. Mueller may find such criminal action; he may not.

We know that the charges against Manafort are for money laundering, not for collusion-related crimes. Papadopoulos and Flynn have pleaded guilty to lying to the FBI.

We also know that the Trump team's repeated assertions that nobody in the campaign had contacts with Russia are not true. We don't know what might amount to collusion and if there was collusion whether specific actions broke specific laws. Presumably, we'll find out, eventually.

It may be that if Trump goes down in this farcical scandal, it will be at his own hand - or, rather, his Twitter finger. On Saturday, he tweeted: "I had to fire General Flynn because he lied to the Vice President and the FBI. He has pled guilty to those lies. It is a shame because his actions during the transition were lawful. There was nothing to hide!"

The tweet implies that Trump knew that Flynn had lied to the FBI before he fired FBI Director James Comey - which could amount to obstruction of justice. The White House obviously is aware that the tweet puts Trump's tail in a crack, which is why they're going with "the lawyer tweeted it."

The blame-the-dog ploy? Really?

At this point, the only absolute certainty is that the Russia investigation will further divide Americans and deepen the cultural and political rifts that were so apparent in the 2016 election. And that will suit the Russians and Vladimir Putin to a T.

Experienced Kremlin-watchers believe that Putin wasn't so much focused on a certain outcome in the presidential election as he was on sowing chaos, undermining Americans' confidence in our institutions, and bloodying the nose of Hillary Clinton.

The operation succeeded beyond all possible expectations - and the ongoing fallout is a gift to the Russians that will keep on giving, way past the holiday season. Which makes Vladimir Putin the sole winner of the 2016 election.