That’s an earnest question to UK readers and domestic observers of British politics. The chatterati on Twitter are oohing and ahhing tonight over the Sun interview that Ed linked earlier, which went live while Trump was having dinner with May and the British establishment. Imagine the NYT doing an interview with Macron on the day of his state dinner at the White House in which he alternately declared Trump’s foreign policy a trainwreck, mused that perhaps Mike Pence would be a stellar president, and suggested that a popular U.S. governor was soft on terror — and then having the interview emerge while he and Trump were dining together. That’s basically where we are tonight with Trump calling May’s Brexit plan a nonstarter, saying that May rival Boris Johnson would be an excellent prime minister (while noting, feebly, that he didn’t mean to pit them against each other), and dumping again on his nemesis, London Mayor Sadiq Khan.

But even the Macron analogy doesn’t fully capture it. Remember, May is in deep trouble politically at the moment. Her Brexit secretary, David Davis, just quit over her Brexit plan, followed by Johnson himself. The Tories are divided over a “hard Brexit” or “soft Brexit,” as May prefers, with catastrophic consequences potentially for her and the party. Now here’s Trump shanking her publicly while he’s an honored guest of the British government.

Instead he believes Mrs May has gone “the opposite way”, and he thinks the results have been “very unfortunate”.

His fiercest criticism came over the centrepiece of the PM’s new Brexit plan — which was unveiled in full yesterday.

It would stick to a common ­rulebook with Brussels on goods and agricultural produce in a bid to keep customs borders open with the EU.

But Mr Trump told The Sun: “If they do a deal like that, we would be dealing with the European Union instead of dealing with the UK, so it will probably kill the deal…

He added: “I would have done it much differently. I actually told Theresa May how to do it but she didn’t agree, she didn’t listen to me.

Here’s the head of the world’s biggest economy telling the Brits not to count on a trade deal after all if they follow May’s plan. Some will say, “Well, he’s right, soft Brexit is unworkable,” but Trump has no difficulty overlooking negotiation gaps when it suits him. He was pure sunshine after the North Korea summit despite the fact that the two sides agreed to nothing meaningful. He could have taken the same approach here with May and soft Brexit, if only as a favor to help protect her politically. “It’s a good start, we’re going to do more talking with the UK and EU,” etc. Why would he knife her?

And so the question: Is that knife wound serious or will it actually help her by building sympathy? I’ve seen it argued both ways tonight. The “serious damage” theory rests on the fact that the sort of “hard Brexit” that Trump wants is already unpopular with Brits. With Trump now the face of it, it’s apt to become even less popular. Divisions among the Tories might deepen; the public might drift away from Brexit of any sort. Labour might benefit in the next election. The right-wing nationalist president might have done his small part here to ensure that the next prime minister is socialist crank Jeremy Corbyn. How’s that for owning the libs?

But there’s another view. The sheer affront of Trump criticizing May while she’s trying to be the cordial host, even going so far as to suggest that his own blueprint for her country’s exit from the EU should have been heeded by the prime minister, might trigger a backlash in May’s favor.

Trump’s favorable rating in the UK is … 17/77, only marginally better than that of the Russian tsar who keeps killing expats on British soil. Remember when Obama went over there before the Brexit referendum to pitch the Brits on voting Remain? Many righties speculated after Remain lost that Obama’s meddling had backfired, as no electorate likes to have a foreign leader sticking his nose into domestic politics. If that’s true, imagine how much more annoyed Brits might be at Trump’s disapproval of May than they were at the comparatively popular Obama’s disapproval of Brexit.

What’s the answer? And why the hell wouldn’t he at least wait until he’s home to dump on May this way?