In an interview with the CBS News magazine "60 Minutes," Steve Schmidt described Palin as "very calm - nonplussed" after McCain met with her at his Arizona ranch just before putting her on the Republican ticket. McCain had planned to name Sen. Joe Lieberman, I-Conn., as his vice presidential choice until word leaked, sparking what Schmidt called political blowback over picking the 2000 Democratic vice presidential nominee.
Schmidt said he asked Palin about her serenity in the face of becoming "one of the most famous people in the world." He quoted her as saying, "It's God's plan."
Palin has not ruled out a run for the presidency.
Schmidt was interviewed by "60 Minutes" for a segment about a new book about the 2008 presidential race, "Game Change," by John Heilemann of New York magazine and Mark Halperin of Time magazine.
Schmidt credited Palin with being a quick study and for giving a great speech at the Republican convention in St. Paul, Minn., but he said it soon became clear that she often was not accurate in her remarks.
"There were numerous instances that she said things that were - that were not accurate that, ultimately, the campaign had to deal with. And that opened the door to criticism that she was being untruthful and inaccurate. And I think that that is something that continues to this day," he said.
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Palin's spokeswoman, Meg Stapleton, has disputed the version of events presented in the reporters' book.
"The governor's descriptions of these events are found in her book, 'Going Rogue.' Her descriptions are accurate," Stapleton said in a statement to "60 Minutes." Stapleton added: "She was there. These reporters were not."
Schmidt conceded that had Palin not been on the ticket, "our margin of defeat would've been greater than it would've been otherwise."
You can also watch the full "60 Minutes" report below: