Being largely left-handed, I am tempted to make something of the fact that not only are John McCain and Barack Obama, the US presidential candidates, left-handed but four of the six US presidents since 1974 have been also. The trend seems too pronounced to be a blip (one expert put the probability at less than one in 10,000) yet its significance is hard to fathom.

Left-handers comprise just over 10 per cent of the US population, similar to most countries, but they are dominating presidential politics in a way that transcends ideology. Gerald Ford, Ronald Reagan, George H.W. Bush and Bill Clinton all favoured the left hand, and Jimmy Carter and George W. Bush the right (Reagan is the most uncertain case: he wrote right-handedly but slapped Angie Dickinson with his left hand in the film, The Killers ). Past contenders Al Gore, Robert Dole, John Edwards, Bill Bradley and Ross Perot are all left-handed, as is Michael Bloomberg, the New York mayor.