John McCain’s surprise choice of Sarah Palin as running mate has provided another fascinating twist in this most engrossing of American presidential campaigns. She has packed a lot into her 44 years. The former Miss Alaska runner-up is pro-gun (she has the hide of a grizzly bear draped over her sofa), antiabortion and is a new breed of Republican politician who challenges the party establishment, stands up to big business and appeals to blue-collar voters. She has just given birth to her fifth child, knowing it would be born with Down’s syndrome, and returned to work three days later. The political calculations behind Mr McCain’s choice are obvious, reinforced by the tributes that Mrs Palin paid to Hillary Clinton in her speech on Friday. The Republicans want to give Hillary supporters, “Democrats for McCain”, another reason to abandon their party allegiance. Some will do so, enticed by the prospect of a woman a heartbeat away from the presidency.

Other voters will turn away for the same reason. The only thing the two share is their sex; Mrs Palin is everything that Mrs Clinton is not. When voters look beyond Mrs Palin’s gender they may see a novice with little experience of national politics and none of foreign affairs. They may decide Mr McCain’s choice is cynical tokenism. Mrs Palin also paid tribute to Geraldine Ferraro, Walter Mondale’s running mate when he was defeated by Ronald Reagan in 1984. If the McCain gamble fails, Sarah Palin will be a similar historical footnote.