Remember Florida’s hanging chads? The bitterness in this year’s Democratic race has not yet hit a point where Bernie Sanders is threatening to run as a third-party candidate. But it is getting perilously close. If it had not been for Ralph Nader’s “spoiler candidacy”, Al Gore would almost certainly have won Florida in 2000 and become president instead of George W Bush.

Mr Sanders could do the same for Donald Trump. The Manhattan billionaire is urging the Vermont socialist to run as an independent in November. Hillary Clinton has rigged the system, says Mr Trump, which is robbing Mr Sanders of what is rightfully his. He should make Mrs Clinton pay the price in the general election.

Could Mr Sanders be blind enough to fall for Mr Trump’s ruse? The answer is maybe. For evidence of that, look at the parallels between Mr Sanders and Mr Nader. The latter, who was then 66, ignored calls to drop out of the 2000 race from those who feared he would split the centre-left vote and hand victory to Mr Bush.