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Sarah Palin may have threatened to sue the publisher and author of a scathing book about her life, but her rise to fame and public prominence since her failed 2008 vice presidential bid could make her case difficult to prove, according to attorneys who deal with similar cases.

Palin’s attorney sent a letter to Crown Publishing, a division of Random House, Monday evening, informing them Palin may sue the publishing house and author of “The Rogue,” Joe McGinniss, “for knowingly publishing false statements” in the book released last week.

But attorneys who handle defamation and libel cases involving public figures say it’s not easy to prove the legal standard of whether an author either knowingly published false reporting or had malicious intent. James Janowitz, a New York attorney who has defended celebrities in defamation cases,  says the bar for Palin’s potential suit ”is as high as it gets.”

“The standard is very high. It requires falsity of the statements of the reports or actual malice, and maybe they could meet that standard, but there is nothing here that would indicate they could,” Janowitz said after examining the letter sent to Crown.

“The reporter or the author is not libelous merely for repeating or reporting false things about the subject, and that’s really the key thing. It doesn’t matter that’s he’s wrong. It matters whether or not he knew what he was writing was false,” Janowitz said. “If he had contrary information or if he made it up and it was false and he had no source at all and he did it for the purpose of either hurting her or boosting the sales of his book when he knew what he was saying was probably false, then he’s in trouble. But that’s a very high bar.”

According to the letter, Palin and her attorney John Tiemessen believe McGinniss did just that and they think they have a smoking gun. The letter alleges that an e mail sent from McGinniss and liberal Alaskan blogger Jesse Griffin proves information in “The Rogue” is false, quoting McGinniss as writing, “nothing I can cite other than my own reporting rises above the level of tawdry gossip. The proof is always just around the corner, but that is a corner nobody has been able to turn.” The letter also claims that McGinniss “ran out of time” to sufficiently source the book.

Conservative blogger Andrew Breitbart posted the email on his web site last week without explanation for how he accessed it or verified its authenticity.

“The revealing email is key as evidence of this defamatory approach to politics through proxies,” a source close to the Palins told ABC News.

However, Janowitz, who is not involved in the Palin case, examined the email and believes it doesn’t come close to proving defamation, if Palin were to go ahead with the suit.

“I don’t see anything in here that suggests there was malice, nor frankly do I see anything that suggests he’s making things up. All he says is there are some sources that I went to,” Janowitz said.

L. Lin Wood, who has represented celebrities in some of the most highly publicized defamation suits in the country, says it would be ”difficult, but not insurmountable” for Palin to prove defamation, adding that the only way to prove “malice” or “reckless disregard for the truth,” is by providing circumstantial evidence. If the email is credible it could be the evidence Palin needs for a successful case, he said. But Palin would have to prove McGinniss “ignored contradictory evidence or purposely avoided finding the truth,” which would be exceedingly difficult to prove.

“It’s a very difficult burden for a public figure, but it can be done,” Wood said. “To be successful as a practical matter you have to have a case where you can easily prove a statement is false because if you have to fight a battle, whether the statement is true or false you are usually not going to be able to meet that burden of meeting actual malice.”

Wood said finding that “serious accusation” that Palin can “easily prove is false” is the first step to a successful defamation lawsuit.

Pursuing a case like this would mean an incredible amount of publicity for Palin and potentially putting  McGinniss’ sources on the witness stand, something the former Alaska governor would likely not want. Orin Snyder, a New York attorney who has also represented many famous people in high profile defamation cases says he doubts Palin truly plans to sue, saying Tiemessen’s letter “is designed as a placeholder to level the playing field on Google as opposed to a serious statement of attention to file a lawsuit.”

“The last thing that someone like Sarah Palin wants is a public lawsuit with wide ranging discovery into the claims made in the book, because what will happen is everyone named or everyone implicated will be deposed, and that’s something that very few people in the public eye want to endure,” Snyder said.

Under Alaskan law, Palin has up to two years from the date of publication to file a suit, but an attorney familiar with the case in Alaska says, “The letter clearly states this is something the attorneys are investigating. It is the start of a long process, not an event. This isn’t a watch your mailbox a complaint is coming next week letter.”

The same source says the reasons to go ahead with the threat is “frankly to preserve evidence.”

“Part of publishing the letter is, without going through the book allegation-by-allegation, line-by-line to basically communicate to people that this book – in case anyone hasn’t noticed the New York Times review or the author’s email – this book is to be generous thinly sourced,” the lawyer said.

The Palin letter alleges McGinnis sent the email in January, and on McGinniss’ blog he wrote in June that he had just finished working on the manuscript. McGinniss did not respond to ABC News requests for comment, but he acknowledged to Slate last week that he sent the email to Griffin six months before he finished his reporting for “The Rogue.”

For their part Crown is standing by McGinnis. Crown spokesman Stuart Applebaum said in a statement, “We are confident that the reporting in THE ROGUE is solid, reliable, and well-substantiated. We stand by our publication and our author.”

The book has been widely panned by critics for using unnamed sources that lob serious charges at Palin and her family. But Kathleen Schmidt, an independent book publicist who has her own firm KMSPR Public Relations and Consulting, has had to deal with similar situations and she says the threat of the suit “has already brought more publicity to the book,” though it probably won’t help book sales tremendously.

“I think in the end it will probably make people a little bit more curious, but I don’t think it’s going to explode book sales,” Schmidt said. “It’s still in a very good position in the Amazon rankings. I don’t think that it’s going to push it over the top.”

Schmidt added that as one of the biggest publishing houses in the country, Random House “doesn’t publish books like these carelessly,” but the “author is responsible for the content he put in it.”

This isn’t Palin’s first legal scuffle in the publishing world.  Last year Harper Collins, the publisher of her book “America  by Heart,”   sued the website Gawker for publishing leaked pages the book. The two sides reached a settlement before the case went to trial.