It looks like President-elect Trump best get moving if he wants an independent Great Britain. That’s what we take from the news that the former Laborite prime minister of Britain, Tony Blair, is going to be agitating against an independent Britain. A friendliness to the idea of an independent Britain is one of the differences between Mr. Trump and the Democrats. Mr. Blair is against independence, to the Devil with what Britons themselves decided in the June referendum.

A report that Mr. Blair is “positioning himself to play a pivotal role in shaping Britain’s Brexit deal” started earlier this month in The Times. The Blair camp tried to dampen such speculation. Now, though, the former prime minister is out with a long interview in the leftist New Statesman, in which he gives the impression that he certainly is going to be part of the effort to stymie British independence (which he campaigned against in the run-up to the June vote).

Mr. Blair couches his argument in all sorts of friendly remarks about Prime Minister May, who also campaigned against Brexit but, once the people spoke, has been vowing to implement it. She’s being challenged in court in a case that may force the matter to a vote in the parliament, where Blair, though no longer in elected office, could fan doubts about independence. Mr. Blair “believes that Brexit can be halted,” as the former premier is paraphrased by the New Statesman.

Brexit, the New Statesman quotes Mr. Blair as saying, “can be stopped if the British people decide that, having seen what it means, the pain-gain cost-benefit analysis doesn’t stack up.” This is the formula that beckons Mr. Trump. He and his administration, combined with the Republican leadership in Congress, will have the chance to enhance the gain part of the analysis through a pro-active of incentives to enhance our special relationship and put Britain at the front of the queue for a trade deal.

Then again, too, Mr. Trump and pro-liberty Tories in Parliament can turn the tables on their anti-independence opponents by reminding Britons that Europe comes with its own costs, which is part of what the Brexit vote was about in the first place. Is anyone in a position to argue that Britain’s relative success is because it has been a member of the EU? If so, why is the rest of the Union in such sad shape? Is there any hope that the EU could be come a liberalizing force within the EU’s own economy?

Not that we’ve heard. Mr. Trump’s call to “drain the swamp” resonates with voters who have watched the European Union metastasize. Nor does Mr. Blair enjoy popular support in the country he once led. “New” Labor, like Clintonism, looks like a spent force in a party that elevates to its leadership a hard-left leader like the Sandersist Jeremy Corbyn. Mr. Blair’s heirs are out and “third way” politics discredited. Mr. Blair’s attempts to return to politics by voiding Brexit is a wake-up call for Mr. Trump.