There was a curious moment in Tuesday’s televised debate between Hillary Clinton and Barack Obama. Mrs Clinton wanted to talk about healthcare and kept talking over the moderator when he tried to change the subject. Mr Obama professed to be mystified by the performance. “The same experts she cites,” he responded, “basically say there’s no real difference between our plans.” That was true, and the overlap extends to almost all their policies.

This is the most furiously contested nomination fight in more than a generation. The two candidates between them have raised $85m (£43m) from supporters in the past month, and Mr Obama has more than a million donors. Americans, even non-Democrats, are riveted by the spectacle. And yet, except for the authorisation to go to war in Iraq (which Mrs Clinton voted for and Mr Obama assailed from his position in the Illinois senate), the positions and voting records of the two candidates are hard to distinguish.