It is hard to think of a demarche quite like the blast President Trump just delivered in respect of Brexit. It came in the form of an interview with the London daily Sun, in which Mr. Trump lit into Prime Minister Theresa May for making a bollix of Britain’s exit from the European Union. He’d told her how to do it, he claimed, and she failed to take his advice. This hit the internet as Mr. Trump was finishing his dinner with Mrs. May, and scores of others, at Blenheim Palace.

Mrs. May herself is facing a political crisis that could yet end her prime ministership. This was precipitated by her betrayal of the Brexit referendum. That happened Friday at the prime minister’s country estate, Chequers, where she decided to seek a so-called “soft” Brexit. It has already precipitated the resignation of key members of her cabinet, including the foreign secretary, Boris Johnson. A backbench rebellion is simmering.

Not only did Mr. Trump direct his remarks at Mrs. May but he warned that if Parliament goes for the deal Mrs. May wants — playing by E.U. trade rules — the logic of a favorable bilateral trade deal with America evaporates. After all, Mr. Trump points out, under the deal Mrs. May is pursuing America would find itself negotiating not with Britain but with Europe. “We have enough difficulty with the European Union,” is the way the president put it.

The one off-note in Mr. Trump’s interview with the Sun is describing Brexit as being about immigration. That’s not our view. We have been covering Britain’s feud with the EU since the 1980s and were among the first to back Brexit. Our support for Brexit has nothing to do with immigration, though we feel it has brought problems as well as human capital to Britain. We back Brexit’s rebellion against European-style statism (and nannyism) and favor British-type freedom.

The best protection for all that is, in our view, true British independence, and a closer British relationship with America. We favor a restoration of sterling and sound money. Our own reckoning is that the Brexit referendum was won when leaders like Nigel Lawson and Boris Johnson stepped up to articulate the high ideals of Brexit. Mr. Trump made clear he gets it. He made a point in his interview with the Sun of speaking well of Mr. Johnson.

It would be an exaggeration to say that Mr. Trump endorsed Mr. Johnson for prime minister, but not much of an exaggeration. Mr. Johnson, Mr. Trump said, would be “a great prime minister.” Whether the Conservative Party will take the hint, we’ll see. There is already furious hand-wringing, in Britain, Europe, and the liberal press here in America, over Mr. Trump’s Brexit blast. We see it as a refreshingly frank interview that could help lead to a new and better partnership of our two countries.