It seemed to me there were two or three spots where McCain's voice sounded like it had a slight, quavering fear. He was working at keeping it under control.

One of these was when McCain said, "I honestly don't believe that Senator Obama has the knowledge or experience and has made the wrong judgements." Youtube <link> at 3:45.

It fits the theory that McCain avoided looking at Obama out of fear. <link> bottom left column.