Teams of Democratic operatives and investigative journalists descended on Alaska yesterday to delve into the private and public life of Sarah Palin, the new and little-known Republican vice-presidential nominee, as fresh questions arose over whether she had been vetted properly by the John McCain campaign.

After the stunning and show-stealing announcement by Mr McCain on Friday that he had chosen the 44-year-old Alaskan Governor as his running-mate, new information emerged over allegations that she tried to use her gubernatorial office to take revenge on her former brother-in-law, part of an ethics investigation that will be released on October 31 – five days before the general election.

If Mrs Palin, a conservative mother of five, ever doubted that landing on a national presidential ticket would open her to the harshest of spotlights and smear tactics, she also awoke yesterday to utterly unfounded internet rumours that her fifth child, born in April with Down’s syndrome, was actually her 17-year-old daughter’s.

When she made her debut speech on Friday she immediately touted her success in killing off the infamous “Bridge to Nowhere”, which would have connected Gravina Island with Ketchikan international airport, a project that had become a nationwide symbol of the wasteful, pork-barrel spending that Mr McCain has made a cornerstone of his campaign.

Yet in a first unsettling revelation – which the McCain camp will hope does not become a pattern – the Anchorage Daily News reported yesterday that when she ran for governor Mrs Palin campaigned on a “build the bridge” platform. The newspaper, in a reference to John Kerry’s alleged “flip-flopping” in the 2004 presidential campaign, said: “Palin was for the Bridge before she was against it.”

With growing concerns about her readiness to be Commander-in-Chief should anything befall Mr McCain, another Alaska newspaper, the Daily News-Miner, wrote in an editorial: “Republicans rightfully have criticised the Democratic nominee, Senator Barack Obama, for his lack of experience but Palin is a neophyte in comparison. Palin is not ready for the top job. It’s clear that McCain picked Palin for reasons of image, not substance.”

On the political talk shows, Democratic surrogates for Mr Obama fanned out to decry Mrs Palin’s lack of experience and her staunch conservatism. She is pro-life, a global warming sceptic and favours drilling for oil in the Arctic National Wildlife Refuge, something even Mr McCain opposes.

Mr Kerry described her as a member of the “flat Earth caucus”, a “Cheneyesque social conservative” chosen to satisfy the Republican base. “John McCain is a prisoner of the right wing, not a maverick,” Mr Kerry said.

Even her mother-in-law, Faye Palin, who said she was still thinking of voting for Mr Obama, sounded sceptical. She said: “I’m not sure what she brings to the ticket, other than she’s a woman and a conservative.”

Yet the surprise choice of Mrs Palin has had an extraordinary impact on the race, with the campaign of Barack Obama scrambling to discover more about her as it calculates how best to go after only the second women to be chosen as a vice-presidential nominee, after Geraldine Ferraro in 1984. Thick dossiers had been prepared on Mitt Romney and Tim Pawlenty – the men believed widely to be the final front-runners – but the file on Mrs Palin is wafer thin.

Although she made a clear bid for suburban mothers and disaffected Hillary Clinton supporters on Friday, her choice has thrilled and energised conservative Republicans and evangelicals, solving in a stroke Mr McCain’s struggle to motivate his base, whose turnout will be crucial in battleground states such as Ohio and Michigan.

The biggest cloud on the horizon is an Alaskan ethics investigation into allegations that, as Governor, she, her husband and her aides, pressured and ultimately fired Walter Monegan, the public safety commissioner, for not sacking her brother-in-law, an Alaskan state trooper involved in an ugly divorce with Mrs Palin’s sister.

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