There was a moment of sweet justice for American conservatives this week as they watched Dan Rather, the long-time CBS newsman, apologise for his report - based on now-disputed documents - about President George W. Bush's military service.

Mr Rather has been a focus of Republican ire on and off since clashing with Richard Nixon in 1974. So when, after nearly two weeks of defending his report, he admitted that he had made a mistake by running a poorly sourced story about Mr Bush's National Guard duty, calling it “an error . . . in good faith and in the spirit of trying to carry on a CBS News tradition of investigative reporting without fear or favouritism”, the conservative glee and indignation was palpable.