If Donald Trump had to choose a favorite word to describe himself, my bet would be on the word “tough.”

In a recent speech to describe his approach to drug abuse, he used a version of “tough” 19 times. He’s tough on trade, tough on the media, tough on porn stars, tough on immigration. Suspected terrorists should be tortured; drug pushers should be executed. No matter the problem, “tough” is Trump’s solution. In a tweet this week, he bragged that in a fight with Joe Biden, the former vice president “would go down fast and hard, crying all the way.”

In every situation, Trump is driven to be seen as the dominant alpha male; his instinct is to belittle, fire, intimidate or otherwise undermine anyone he perceives as a threat to that status.

There is, however, one glaringly obvious if inexplicable exception to that policy. It involves Russian dictator Vladimir Putin.

Under Putin’s leadership, Russia has tried to intervene in our elections, the very core of self-government, and he shows every sign of preparing to do so again. He has brazenly launched a nerve-agent attack on the soil of our best ally. He has unleashed his army of hackers to break into systems controlling our nation’s power grid, pipelines, dams and vote-counting. In Syria, Russian mercenaries have directly attacked U.S. forces, and under Russian protection, the Syrian government has resumed the use of chemical weapons against its own people.

Trump’s response? This week, despite strong advice from his staff, he called Putin to congratulate him for winning a clearly fraudulent election; despite strong advice from Trump’s staff, he said nothing about the nerve-agent attack in Great Britain. “Getting along with Russia (and others) is a good thing, not a bad thing,” tweeted a man who usually treats “getting along with others” with disdain.

Of all the weirdness that we’ve witnessed in this administration, nothing is more bizarre and inexplicable than this craven groveling. In the one arena in which toughness might be useful, in which our allies, our intelligence community and our national security experts all agree that confrontation is essential, Trump has proved docile to the point of submission.

Such behavior contradicts everything that we think we know about the man, everything that he asks us to think of him. On the surface, it even seems at odds with what we know to be his powerful sense of self-preservation. Facing an investigation into possible Trump-Russia collusion, it would seem to be in Trump’s own self-interest, legally and politically, to at least pretend to be taking strong action against his alleged co-conspirator.

Even then, he does not and cannot.

That leaves us with one of two explanations. The first is that Trump knows something that we do not, so that behavior that looks self-destructive from the outside is actually self-preservation from Trump’s point of view. Put another way, Trump grovels and submits before Putin because he has no choice, because for some reason he dare not risk Putin’s anger.

The second explanation draws heavily from psychology. It suggests that Trump’s tough-guy act in every other aspect of his life has indeed been just that, an act to cover his deep insecurities, and that Putin’s bare-chested, horse-riding, judo black belt act has exposed Trump’s true self. Weird, but …

If there are other explanations, I’m open to hearing them, because the two that we have on the table don’t bode well for our continued role as a global leader under this president.