But Trump’s squandered economic opportunities are, of course, secondary at this point to his de facto self-impeachment.

Just a few weeks ago it seemed that Trump would skate on charges both of colluding with Russia to subvert the 2016 election and of obstruction of justice; the Mueller report was basically a bust, partly because the story was complicated, partly because of Robert Mueller’s diffidence.

But Trump has managed to make things clear enough for everyone to understand. First he demanded that foreign regimes produce dirt on domestic political rivals, not just in phone calls but right there on camera. Now he’s engaged in a crude, obvious effort to stonewall the House impeachment inquiry that is clearly an impeachable offense in itself.

Why did he hand the defenders of democracy so much ammunition? Partly he seems to have gotten high on his own supply — he actually seems to believe the bizarre conspiracy theories his supporters drum up to excuse his actions. Also, he evidently lacks any kind of self-restraint. Even if he considers any effort to hold him accountable a form of treason, he should have known better than to blurt it out in public.

So Trump’s own actions explain why a vote to impeach, which seemed unlikely just a few weeks ago, now looks almost inevitable. Conviction in the Senate is still unlikely, but not as impossible as it once appeared.

The larger point is that if Trump were cannier and more self-controlled, the march to autocracy might well be unstoppable. He has the backing of a party whose elected representatives have shown no sign of democratic scruples. He has de facto state media in the form of Fox News and the rest of the Murdoch empire. He has already managed to corrupt key government agencies, including the Justice Department.

Indeed, these advantages are so large that the assault on democracy may yet prevail. The only reason it might falter is, as I said, Trump’s own deficiencies.

It says a lot about the modern G.O.P. that the party is still solidly behind a man so obviously, grotesquely, not up to the job (although some rank-and-file Republicans now back an impeachment inquiry). But those of us who want America as we know it to survive should be grateful that Trump is so immature and incompetent. His character flaws are the only thing that gives us a fighting chance.

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