Sarah Palin's attacks on Barack Obama's patriotism provoked a spike in death threats against the future president, Secret Service agents revealed during the final weeks of the campaign.

    Sarah Palin's attacks on Barack Obama's patriotism provoked a spike in death threats against the future president, Secret Service agents revealed during the final weeks of the campaign.

    The Republican vice presidential candidate attracted criticism for accusing Mr Obama of "palling around with terrorists", citing his association with the sixties radical William Ayers.

    The attacks provoked a near lynch mob atmosphere at her rallies, with supporters yelling "terrorist" and "kill him" until the McCain campaign ordered her to tone down the rhetoric.

    But it has now emerged that her demagogic tone may have unintentionally encouraged white supremacists to go even further.

    The Secret Service warned the Obama family in mid October that they had seen a dramatic increase in the number of threats against the Democratic candidate, coinciding with Mrs Palin's attacks.

    Michelle Obama, the future First Lady, was so upset that she turned to her friend and campaign adviser Valerie Jarrett and said: "Why would they try to make people hate us?"

    The revelations, contained in a Newsweek history of the campaign, are likely to further damage Mrs Palin's credentials as a future presidential candidate. She is already a frontrunner, with Louisiana Governor Bobby Jindal, to take on Mr Obama in four years time.

    Details of the spike in threats to Mr Obama come as a report last week by security and intelligence analysts Stratfor, warned that he is a high risk target for racist gunmen. It concluded: "Two plots to assassinate Obama were broken up during the campaign season, and several more remain under investigation. We would expect federal authorities to uncover many more plots to attack the president that have been hatched by white supremacist ideologues."

    Irate John McCain aides, who blame Mrs Palin for losing the election, claim Mrs Palin took it upon herself to question Mr Obama's patriotism, before the line of attack had been cleared by Mr McCain.

    That claim is part of a campaign of targeted leaks designed to torpedo her ambitions, with claims that she did not know that Africawas a continent rather than a country.

    The advisers have branded her a "diva" and a "whack job" and claimed that she did not know which other countries are in the North American Free Trade Area, (Canada and Mexico). They say she spent more than $150,000 on designer clothes, including $40,000 on her husband Todd and that she refused to prepare for the disastrous series of interviews with CBS's Katie Couric.

    In a bid to salvage her reputation Mrs Palin came out firing in an interview with CNN, dismissing the anonymous leakers in unpresidential language as "jerks" who had taken "questions or comments I made in debate prep out of context."

    She said: "I consider it cowardly. It's not true. That's cruel, it's mean-spirited, it's immature, it's unprofessional and those guys are jerks if they came away taking things out of context and then tried to spread something on national news that's not fair and not right."

    She was not asked about her incendiary rhetoric against Mr Obama. But she did deny the spending spree claims, saying the clothes in question had been returned to the Republican National Committee. "Those are the RNC's clothes, they're not my clothes. I asked for anything more than maybe a diet Dr Pepper once in a while. These are false allegations."

    Speaking as she returned to her native Alaska, Mrs Palin claimed to be baffled by what she claims was sexism on the national stage. "Here in Alaska that double standard isn't applied because these guys know that Alaskan women are pretty tough, on a par with the men in terms of being outdoors, working hard," she said.

    "They're commercial fishermen, they're pilots, they're working up on the North slope in the oil fields. You see equality in Alaska. I think that was a bit of as surprise on the national level."