Sarah Palin joins her buddy Beck at Fox News

Rupert Murdoch's Fox broadcasting company today signed Sarah Palin as a regular pundit and occasional host on its controversial Obama-bashing cable news network. It means Palin will be sharing a platform with the rightwing TV hosts - Glenn Beck and Bill O'Reilly - who have supported her through her period as John McCain's Republican running-mate in the 2008 presidential election and throughout the scandals and rumours that have dogged her ever since.

When Palin resigned as governor of Alaska last summer it created a storm of conjecture that she was preparing for a run at the presidency in 2012. The Fox contract will give her the exposure she needs if she really aims to pursue a presidential bid. Currently she makes most of her political pronouncements on her Facebook page.

According to the Washington Post, she will appear as a commentator on various shows and host an occasional programme examining inspirational tales involving ordinary Americans. She will not be given her own show. Cynics say that, given the famous gaps in her knowledge, and some chaotic TV appearances in the past, a show would be beyond her.

While Palin is a figure of fun in the liberal media, she enjoys a strong conservative base which came out to buy her recently published memoir, Going Rogue, driving it straight to the top of the bestseller lists. On a carefully managed book tour, thousands came out to greet her.

These faithful readers will not be impressed, however, by the publication this week of another new book concerning her run at the vice-presidency in 2008.

Game Change, a racy campaign trail book by John Heilemann of New York magazine and Mark Halperin of Time magazine, portrays Palin as not just ignorant of world affairs but as a woman whose mood swings are so wild that some observers believe she is mentally unstable.

"One minute, Palin would be her perky self; the next she would fall into a strange blue funk," according to the authors.

On the morning of her fateful interview with Katie Couric of CBS, when Palin was let off the leash by her McCain minders for the first time, she would not respond to attempts to prepare her for the interview. She was having her face made up and her eyes were "glassy and dead" say the authors.

"As they were about to set off to meet Couric, Palin announced 'I hate this makeup' - smearing it off her face, messing up her hair, complaining she looked fat," the book relates.

The interview was a disaster and over the following days Palin stopped eating or sleeping, and drank only a half a can of diet soda a day.

"When her aides tried to quiz her she would routinely shut down - chin on her chest, arms folded, eyes cast to the floor, speechless and motionless, lost in what those around her described as a kind of catatonic stupor," the book says.

At Fox, Palin will have the platform from which to get back at Heilemann and Halperin. She'll be among friends, not least her buddy Glenn Beck who not only shares her beliefs - anti-abortion, anti-gun control, pro-free market - but also famously called Obama a racist.

In an interview with Newsmax last year, Palin was asked whether she would consider Beck as her running-mate if she decided to go for the presidency in 2012. "Glenn Beck I have great respect for," she responded. "He's a hoot. He gets his message across in such a clever way. And he's so bold ­ I have to respect that. He calls it like he sees it, and he's very, very, very effective." ·