At Washington’s annual Gridiron dinner with the media two years ago, Barack Obama converted a recent falling-out with fellow senator John McCain into material for a humorous speech. The older senator had publicly scolded the freshman for behaving with “disingenuousness” over an ethics bill on which they had earlier been collaborating.

To the tune of “If I only had a brain”, Mr Obama sang: “When a wide-eyed young idealist/ Confronts a seasoned realist,/ There’s bound to be some strain. With the game barely started,/ I’d be feeling less downhearted/ If I only had McCain.”