Two exchanges distilled the theme of the night -- Biden's ability to deflect focus from the administration's weaknesses and shower Ryan with every imaginable line of attack in a hail of blows.

First, Biden wriggled out of what should have been the toughest question, on Libya, claiming, despite State Department testimony to the contrary, that the administration hadn't known extra security was needed at the consulate where the American ambassador was recently killed. But rather than pin him down on it, Ryan got tangled in a bruising back-and-forth over whether a Romney administration would start unnecessary wars, as Biden claimed. The topic should have been an opportunity for Ryan, but he failed to maximize it and found himself essentially defending the dismally unpopular foreign policy of George W. Bush instead.

Next, in a segment that surely had liberals standing and cheering, Biden went on a lengthy tirade against Romney's comments about the 47 percent of Americans who don't pay federal income taxes -- something the president never mentioned in last week's debate:

But it shouldn't be surprising for a guy who says 47 percent of the American people are unwilling to take responsibility for their own lives. My friend recently in a speech in Washington said "30 percent of the American people are takers." These people are my mom and dad -- the people I grew up with, my neighbors. They pay more effective tax than Governor Romney pays in his federal income tax. They are elderly people who in fact are living off of Social Security. They are veterans and people fighting in Afghanistan right now who are, quote, "not paying any tax." I've had it up to here with this notion that 47 percent -- it's about time they take some responsibility here. And instead of signing pledges to Grover Norquist not to ask the wealthiest among us to contribute to bring back the middle class, they should be signing a pledge saying to the middle class we're going to level the playing field; we're going to give you a fair shot again; we are going to not repeat the mistakes we made in the past by having a different set of rules for Wall Street and Main Street, making sure that we continue to hemorrhage these tax cuts for the super wealthy.

Ryan shot back, "I think the vice president very well knows that sometimes the words don't come out of your mouth the right way." Biden grinned his wide, bright-white, triangular smile. "But I always say what I mean," he said. "And so does Romney."

There was plenty more where that came from. Biden nailed Ryan, gleefully, for having asked for stimulus funds for his constituents. He ridiculed Ryan's attack on "green pork." Ryan got some good shots in on Medicare, but then found himself defending privatizing Social Security after Biden turned the tables. "Jack Kennedy lowered tax rates," Ryan said. "Oh, now you're Jack Kennedy?" Biden said. "Ronald Reagan -- " Ryan began. "This is amazing," Biden grinned. Just as Republicans last week felt someone was finally taking to task the president they'd always seen as a fraud, Biden effectively channeled the left's bottled-up frustration with the Romney-Ryan argument.