Palin is working with a cadre of McCain's aides, The New York Times reported Tuesday.
Palin's arrival at the Republican presidential nominee's ranch in Sedona, Ariz., Monday to prepare for the forum with Democratic vice presidential nominee Joe Biden indicates concern that her popularity is waning, the Times report said.
"I think she has pretty thoroughly -- and probably irretrievably -- proven that she is not up to the job of being president of the United States," David Frum, a former speechwriter for President George Bush and now a columnist, told the Times.
Polling indicates the number of Americans who think Palin is not fit to be president has increased since McCain introduced her as his running mate, the Times said.
But a series of missteps -- including her performance in a much-publicized interview with CBS anchor Katie Couric -- could help Palin by lowering expectations for her in the debate, one state GOP leader said.
"The style of Sarah Palin is going to amaze people," said Ron Carey, chairman of Minnesota's Republican Party. "She is going to be able to amaze people with the substance she is going to deliver."