I shared my prediction on the consequence of the video tape in The Fix blog on the WaPo website today.
It's a prediction, and predictions are hard, especially of the future. However, I think that this is the likely result:
The needle won't move very much, but it puts a ceiling on Romney support.
The undecided won't suddenly swing to Obama, but they have one more reason to not swing to Romney.
Romney voters won't leave him, but they will be slower to argue with their friends who are undecided.
Obama voters won't -- of course -- move, but they have one more reason for backing their man.
One thing I didn't mention was that enthusiasm normally builds up as the election gets closer, and Ii don't see Romney enthusiasm building.