Just five years ago, Barack Obama was still a local politician in Illinois, preparing for a run for the US Senate. His office wall in Chicago at the time was decorated with the famous picture of Muhammad Ali standing over Sonny Liston, after knocking him out in a heavyweight title fight. Ali famously boasted that he could “float like a butterfly and sting like a bee.” But now that Mr Obama is president, he seems to float like a butterfly – and sting like one as well.