Echoing Barack Obama's catchline, "Yes, we can", -Hillary Clinton's rallies are increasingly interrupted by chants of "Yes, she can". But with only a day left before 22 states vote in the Super Tuesday primaries, "Maybe she won't" is the fear haunting her campaign.

In the space of a fortnight, Mrs Clinton's national lead over Mr Obama has been reduced from a 20-point margin to a dead heat, according to the latest opinion polls from Gallup and Reuters. Some show that Mrs Clinton's commanding lead in California - the largest of the 22 states to go to the polls tomorrow - has also been sharply cut, despite her continuing strength among Hispanic voters.