Two people close to the campaign, addressing her difficulties, said she had been stuffed with facts as if preparing for an oral exam and had become nervous and unnatural in the few interviews.

Advisers said she was a diligent worker and was frequently up until the small hours of the morning in her hotel room trying to cram as much information as possible before the debate.

“I think she has to be careful not to be overprogrammed for the debate,” said Robert T. Bennett, the Ohio Republican chairman. “I think she’s a lot brighter than people are giving her credit for.”