"There's one Sarah who you see in public, upbeat. But the other Sarah was the one that frightened (members of the campaign)," John Heilemann, co-author of "Game Change," said on "60 Minutes."
"It was someone whose eyes were kind of glazed over, who was literally not responding to questions, who was keeping her head down."
Steve Schmidt, the top strategist for Sen. John McCain's White House bid, told the CBS News program he had received a desperate call from the person responsible for preparing Palin for the debate.
"He told us that the debate was going to be a debacle of historic and epic proportions. He told us she was not focused, she was not engaged, she was really not participating in the prep," Schmidt said.
Heilemann, a New York magazine writer, said Palin's tutors were "literally taking her through, 'This is World War I, this is World War II, this is the Korean War, this is the -- how the Cold War worked. This is the new war on terror.' They're trying to teach her everything because Steve Schmidt had gone to them and said, 'She knows nothing.'"
Schmidt recalled the former Alaska governor couldn't get Biden's name right.
"She kept confusing Joe Biden's name with Obama's, calling him 'O'Biden,'" he said. "You certainly cannot be in a position where you walk out onto the stage and, you know, refer to him repeatedly on national television as Senator O'Biden."
Hence, Palin's pre-debate request: "Hey, can I call you Joe?"
When McCain chose her as running mate, Schmidt said: "She was very calm, nonplussed. I said, 'You don't seem nervous at all about this.' And she said, 'No, it's God's plan.'"
Schmidt gave Palin high marks for her speech at the Republican National Convention in St. Paul, Minn. But he said he soon realized she often made inaccurate statements.
"There were numerous instances that she said things 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."
CBS said Palin declined to comment for the "60 Minutes" story.