Every now and then a stopped clock is right. Speculation about a presidential bid by Michael Bloomberg, the former mayor of New York, is a quadrennial affair. It never happens because Mr Bloomberg can do the maths.

Third party candidates do not win in America — they usually come away with nothing. But 2016 is different. The political laws of gravity are in suspension. If there was ever a moment for a New York billionaire to roll the dice, now would be it. The question is what would happen if he did.

According to those around him, the prospect is not academic. “People here are talking about nothing else,” says a friend who works at Bloomberg’s news operation. The three-times mayor of New York has commissioned polls to look at how he would fare in a three-way race between Donald Trump and Hillary Clinton. Should Bernie Sanders be the Democratic nominee, Mr Bloomberg’s temptation would grow. Who then would speak for voters who believe in free trade, internationalism and global alliances? Not Mr Trump, for sure. Or Mr Sanders. Enter Mayor Bloomberg.