BUSH BOOKS

Laura Bush, a former librarian, also has expressed interest in writing a book and has the advantage of being popular.

Agent Gary Morris of the David Black Literary Agency said intrigue about Laura Bush is linked to the success of Curtis Sittenfeld's "American Wife," a fictionalization of her life.

Palin, who rallied conservatives when presidential candidate John McCain added her to the Republican ticket, could be the real prize, some experts say.

"There are half a dozen publishers that would zealously bid on a Palin book," said Robert Weil, executive editor at WW Norton. "Some agents say she could sell for $7 million."

"Every publisher and a lot of literary agents have been going after her," said Jeff Kleinman, an agent at Folio Literary Management.

Many presidential candidates write books before running – Obama's "The Audacity of Hope" was a best-seller – and recent former presidents have published with mixed results.

Clinton's "My Life" was a big earner for Alfred A Knopf, an imprint of Random House, largely because he worked tirelessly to promote it.

But Ronald Reagan's "An American Life" was seen in the industry as a big loser for Pocket Books, a division of Simon & Schuster, part of CBS Corp.