Fair enough. I'd only make two points in response to that -- which, again, are mere speculation at this point.

First, those were presidential debates which showed the demeanor of the main candidates who will stand out in people's minds. Any "meanness" of the running mates may have less of an effect on those impressions of the ticket -- it's hard for me to say at this point. Admittedly, I don't know my history of vice presidential debates well enough to speak much on this issue.

Second, the Romney-Ryan ticket clearly had the momentum entering this debate. I don't think that Biden's approach will accelerate that; my guess, which is nothing more than conjecture, is that it may have muddied the waters a bit. I wonder, at least, if this performance may have given voters a reason to doubt the conclusions that they drew after the first presidential debate. Romney looked so dominant over Obama in round one, but Ryan looked comparatively timid here, which might put a damper on the initial impression that the Romney-Ryan ticket was stronger than the Obama-Biden one. (That's assuming, of course, that they put any stock in the running mate's strength as showing the capabilities of the ticket as a whole.)

I just think that if anything, this debate will put the brakes on Romney's momentum, keeping him from running away with this. That's just my guess, and time will tell whether the polls validate my impression or whether they prove me wrong.