I think that Jon's scoring the debate was pretty close, though I slightly prefer Charles Krauthammer's take. If you read the transcript, it was a tie. On radio, Biden wins. On TV, Ryan wins. I would add that all of these involve small margins.
Ryan seemed to tire out near the end. He could have done much better on the religion and abortion question. Biden exposed more problems overall, due mostly to the fact that he is the incumbent and has an actual record to defend. I note one glaring admission: he says that "we", meaning, presumably, the President and himself, were not told that the consulate in Benghazi requested more security. Isn't this something the President should know? Here's my suggestion for an ad:
Under President Obama, thousands of lethal weapons were delivered to Mexican drug lords by the U.S. Government. But don't blame the President. He didn't know anything about it. Under President Obama, the State Department refused to provide the security that the consulate in Benghazi pleaded for just before the attack that killed Ambassador Stevens. But don't blame President Obama. He didn't know anything about it.
I doubt that this debate will have much impact. CNN's spot poll gave Ryan the victory 48-44%. With a 5% margin of error, Wolfe Blitzer called that a tie, but by that logic anything short of a blowout for one debater would be a statistical tie. CBS did an online poll that gave the victory 50-31% to Biden. It's hard to game those two polls.
I am guessing that post debate polls in the next couple of days will show something like a tie. That may help the Obama campaign "staunch the bleeding," if only because it cleanses the pallet of the first debate taste. Only a blowout for either side would have been really significant.
A lot of weight rides on the last debate. How much will depend on the polls over the coming week.
UPDATE: here is a list of instant polls from Michael Barone:
The instant polls: CNBC had it Ryan 56%-36%, CBS Biden 50%-31%, CNN Ryan 48%-44%, AP Ryan 51%-43%.
If you are inclined to think that the instant polls are not worth taking seriously, I would remind you that the polls taken after the last debate were dead spot on. This list suggests that Ryan won by a large margin where it counts.