For awhile I thought this post written last night was all for naught. POTUS wasn’t going to seize the opportunity to topple one of his most ardent Republican critics after all. The mystery might linger forever: Why, with Mark Sanford battling for his political life and his seat in no danger of going to a Democrat, didn’t Trump administer the coup de grace by endorsing his opponent, Katie Arrington?

But there is no mystery after all. The endorsement has come.

And it’s a doozy:

https://twitter.com/realDonaldTrump/status/1006630395067039744

Everyone gets the Argentina reference, right? Good for POTUS for championing the idea that politics is better off without, um, men who cheated on their wives.

Sanford’s libertarian-minded friends in the GOP caucus didn’t care for the tweet:

.@MarkSanford’s job is to support and defend the Constitution. He’s one of the most principled, consistent, and conservative members of Congress I’ve ever known. And unlike you, Mark has shown humility in his role and a desire to be a better man than he was the day before. https://t.co/zNYKb5WKmH

— Justin Amash (@justinamash) June 12, 2018

If it makes Amash feel better, I think Dan Scavino — I mean POTUS — was just feeling “punchy” on Twitter this afternoon:

https://twitter.com/realDonaldTrump/status/1006640694264397824

Actually, there is still a small mystery remaining about Trump and Sanford. Why the hell did Trump wait so long to post his Arrington endorsement? It’s primary day! Polls have been open in South Carolina since 7 a.m. ET and will close at 7 p.m. His tweet went live around 4, giving South Carolinians in Sanford’s district just a few hours to rush down to the polls and MAGA by voting out the Trump critic. If Scavino really is manning the controls of Trump’s account today, he could have posted the Arrington endorsement bright and early this morning. Or, if that would have looked unseemly because Trump was still busy with Kim Jong Un, he could have posted it this weekend, all the better to give local news in South Carolina time to cover it and amplify it. Waiting until voting is almost over to try to take Sanford out is pretty Trump even for Trump.

And he’s taking a gamble in doing it. If Sanford squeaks through because POTUS’s endorsement came late, Trump’s enemies will crow that the president has less influence than he thought over a Republican House primary, even in a very red district.

One other thought, from the “be careful what you wish for” files: If Sanford gets KO’d tonight by Arrington he’ll be a man with time on his hands, who knows what it’s like to run a campaign, and who’ll have made a new post-scandal name for himself as a principled fiscal conservative in an age when most of the party is in hock to POTUS politically. He is, in other words, a prime candidate to be recruited for a primary challenge to Trump in 2020, filling the Jeff Flake role of opposition leader in case Flake doesn’t want it himself. Right, granted, he wouldn’t stand a chance of winning, but that’s not the point. The point would be to sharpen the contradictions between Sanford-style conservatism and Trump-style Republicanism and force righty voters to take sides. Trump wins easily but maybe not unscathed, and the damage done to him could hurt him in the general election. It might be better for POTUS in the long run if Arrington fell short tonight and Sanford continued to busy himself with being not-very-relevant in the House.