@engineer,
McCain's main talking point during the first debate was "what Obama doesn't understand is blah blah blah...." As he repeated those words, the audience scoring went below the middle line.
You can almost bet that his talking point during the second debate will be something like "Obama doesn't have the right kind of experience to blah blah blah..." The failure of this kind of rhetoric is that most will see through it as his diversion from the important issues of our day - like the economy. If they show the audience scoring, poor McCain is going to go below the bottom line.
Also, in his desperation, he's going to say things similar to "Obama pals around with domestic terrorists..."
All Obama needs to do is tell us about how he will work on our economy - in detail, and ignore McCain's negative rhetoric.