We all know that vice-presidential debates don't matter, or at least that's what we knew until last night. This one, however, may turn out to matter quite a bit, even if it doesn't produce any major movement in the polls, for two reasons. The first is the obvious one: it has already made despondent Democrats feel a lot better. They wanted to see their guy aggressively take on the other side, and that's exactly what they got. Markos Moulitsas of DailyKos probably spoke for most Democrats when he wrote, "Tonight felt great, didn't it? ... we base liberals are happy again, which means we'll be productive bees because no matter what some of you claim, no one likes to work hard for the team that is 10 points down (or feels that way)."
Conservatives, on the other hand, are unanimous in their judgment that Biden was overbearing and mean. Last night on Fox, Brit Hume called him "a cranky old man." "Biden Bombed," reads the Fred Barnes piece on the Weekly Standard web site. "Classless Joe," says the National Review. They aren't completely wrong—Biden certainly interrupted Ryan more than was necessary, and could have dialed back the smiling and head-shaking a bit. But his unrelenting aggressiveness was just what Democrats wanted to see, and will no doubt spur President Obama to try to avoid looking somnolent by comparison.
The second reason the vice-presidential debate matters is that it sets the stage for the final two presidential debates in an important substantive way. To see why, let's look back at one of the things many observers found odd about the first Obama-Romney debate, that Obama never brought up the "47 percent" video. Many put it down to timidity on Obama's part, but my interpretation was that Obama may have calculated the following: We're already killing him with ads on this, and he's surely prepared a great response for when I bring it up, so let's not give him the chance to turn it to his advantage. But what we saw last night was that it turns out that the Romney campaign doesn't have a great response to the question. It's true that Ryan had a practiced zinger—"I think the vice president very well knows that sometimes the words don't come out of your mouth the right way"—but that's a response that sounds good for a minute but doesn't change how people think about the matter. The substance of Ryan's response, which was that Romney is "a good man" who gives a lot of money to charity, was met by Biden with exactly the right counter, which is that it doesn't matter whether Romney is a good man in his personal life if the policies he advocates aren't good for millions of people.
And this kind of thing happened again and again in the debate: Biden would attack Romney, and Ryan would offer a middling defense that amounted to little more than a repetition of the same things he and Romney say on the stump every day. A large part of debate preparation is practicing your responses for the attacks you know are going to come, and if the Romney campaign had fantastic answers to the criticisms about their tax plan, about Medicare, about Iran, or about any number of other issues, Ryan would have offered them. But he didn't.
So Barack Obama probably watched this debate and concluded that Mitt Romney doesn't have any more surprises up his sleeve. Obama has said that he was shocked in the first debate when Romney began unveiling his new moderate persona and didn't quite know how to react. I wouldn't be surprised if there's some truth to that. But now there isn't anywhere else for Romney to go. Biden hit Ryan with everything he had, and nothing Ryan said could make Obama the least bit uneasy about what Romney will do when they meet again on Tuesday night. So like his supporters, Obama probably came away from last night substantially more uplifted and confident than he was 24 hours ago, and that could be the real impact of the vice-presidential debate.