This group was largely Obama voters who thought of themselves as undecided.
What does that tell you?
If you already voted for somebody, but the next time around you consider yourself undecided, that shows that The One you voted for has let you down. You can't bear the thought that your prior vote was wrong. You WANT to believe in your man, but your brain says no. So you become "undecided" to see what the other guy has.
This debate confirmed everything for these people that they already knew.
The debate didn't show them anything major. There was no gotcha thing that Romney came up with.
These people saw things in Zero that they already knew.
I think 2 things happened. Romney eased these peoples fear and hesitation of him. And Obama confirmed in them their mistrust of him.
These people were already on the fence. Romney just held out a hand to help them step down. And Obama just gave them the slightest push to move them.