Barack Obama has disclosed – even if he didn’t mean to, exactly – that when he leaves the Oval Office at the start of next year, he and his family plan to stay in Washington DC for at least two more years so his younger daughter, Sasha, now 14, can finish school.
The revelation has startled the capital. By convention, presidents are expected to give their successor, of whichever party, space. If history has anything to say on the matter, that should be a Republican next time. And that would suggest a President Donald Trump. The town may not be big enough for the two of them.
Woodrow Wilson was the last to break this code, in 1921, but he was unable to move anywhere else because of his poor health.
Even the British comply with the same code: when a UK ambassador ends their stint in Washington, they are required to leave town and not return for at least a year, regardless of any job offers they may meanwhile have received.
But Mr Obama, who let this decision slip at a lunch with Obamacare beneficiaries in Milwaukee, is only being a selfless father. He wants to give Sasha continuity, by making it possible for her to remain at one of the most exclusive private schools in the land, Sidwell Friends. Her sister, Malia, 17, will be graduating from Sidwell this year and is expected to go to university in the autumn.
There has been endless speculation over where the Obamas would settle once his presidency ends, much of it focused on whether it will be New York, Chicago or Los Angeles. Many expect him to spend considerable time on the Obama Foundation at the University of Chicago.
Of course, Mr Trump still has actually to win the Republican nomination, and the last few days have not been kind to him. And even if he does secure it, the Democrats fancy their chances of sending Hillary Clinton to Pennsylvania Avenue – for whom having Mr Obama close at hand might almost be reassuring.
They used to say of Ms Clinton that if you elected her, you’d get two presidents for the price of one. In 2016, it could be three for the price for one: a Hillary-Bill-Barack administration.