Supporters of Clinton are quick to point out that she is five years younger than Biden and only Ronald Reagan has been as old as 74 when elected, and that was for his second term in 1984. They also note that in 2008 Biden said that Clinton “might have been a better pick than me” for vice-president.

Biden does not even have the upper hand over Clinton in his birthplace, in part because she also has deep family connections there. Her great-grandparents came to Scranton in the 1880s from Wales, her grandfather worked as a boy at the Scranton Lace Factory and her father is buried in the city.

And while Obama’s words might have seemed an imprimatur, few in Washington will take them at face value. While Obama likes to portray Biden as “the scrappy kid from Scranton who beat the odds”, in large part this is to trade on Biden’s appeal to blue-collar whites, who have been slow to warm to the president’s aloof manner.

Biden’s blunders are legendary, and eagerly recounted by Republicans. The garrulous former senator for Delaware, who served in Congress for 36 years, once told a wheelchair-bound state senator: “Stand up, Chuck — let ’em see you.”