Pundits frequently talk about the "narratives" that campaigns are trying to advance. They are like one-sentence blurbs to sell movie ideas to studios -- they have to have immediate punch and portability... you have to get the idea without having to spend much time on it, and you have to be able to transmit the idea with little effort in as few bytes as possible. Romney is rich and therefore doesn't care about average people. Obama is incompetent and not up to the job of President. You get the idea.
After the first debate, the narrative Democrats tried to advance was "Romney lied." The narrative that Republicans tried to advance was "Obama can't defend his record." The narrative that won out in the post-debate spinning was essentially a media creation -- "Obama mailed it in, Obama didn't want to be there, Obama was unprepared" -- all of which was a way of saying that there's nothing wrong with the policies of the Obama administration, just Obama's presentation. But, in the end, it was a one-sentence, one-idea meme that defined the event and reduced it to a blurb.
So the question coming out of the VP debate is what the "narrative" will be. And it's there that I think the Democrats have a real problem. Ryan didn't do a great job in my view in articulating conservatism, and he was bland, but what he did accomplish was to be serious, respectful, adult, competent and unthreatening. There's nothing there to create a narrative around. "Ryan lied." I don't see that working... he's too nice. "Ryan's stupid," a la Sarah Palin. That won't work either... he's known as a policy wonk, and everyone in the media buys into that idea of him. So the narratives the Democrats usually want to put forward won't work.
But then there's Joe Biden. He's a walking narrative, and it's very easy to see what the blurb coming out of the debate will be. Biden was rude. Biden interrupted. Biden laughed at the wrong time. Biden was out of control. Biden was nasty.
None of those narratives play well with the independent voter or the moderate female voter. Remember the suburban soccer mom? What does she tell her kids? "Play nice." "Be a good sport." "Don't interrupt." The suburban soccer mom will hate what she hears about Biden's performance.