Stylistically, McCain talked to moderator Jim Lehrer while Obama talked into the camera. So we viewers watched McCain debate and Obama speak directly to us. The stylistic difference left us with a sense that Obama is the more focused and compelling candidate.
McCain scored points by pinning the naive label on Obama and warning about the danger of his policies, but that impression was counteracted by the seeming knowledge and seriousness of Obama's approach. He didn't look or sound like a naif.