Ryan argued that the attack on the U.S. Consulate in Benghazi, Libya, was a symptom of the "unraveling of the Obama foreign policy," saying that the administration had failed to secure the consulate and had blamed protesters for what turned out to be a terrorist attack. Obama has also sent conflicting signals about the administration's determination to stop Iran from obtaining nuclear weapons, Ryan said.
Biden sought to turn the tables, stressing that Ryan and Republican presidential nominee Mitt Romney have expressed support for the economic sanctions the administration has imposed on Iran, and could not say what they would do differently. He also ridiculed Ryan for suggesting that the United States should not have set a definitive deadline of 2014 for pulling troops out of Afghanistan.
"You'd rather we be sending in more Americans to do the job?" Biden said. "It's time for the Afghans to take responsibility for the security of their country."
On domestic issues, Biden brought up the video of Romney at a fund-raiser talking about the 47 percent of Americans who pay no income taxes as "victims" who depend on the government.
"I've had it up to here with this notion that, '47 percent, it's about time they take some sort of responsibility here,' " Biden said.
Ryan responded with a quip alluding to Biden's reputation for verbal miscues.
"Mitt Romney's a good man. He cares about 100 percent of Americans in this country," Ryan said. "I think the vice president very well knows that sometimes, the words don't come out of your mouth the right way." That drew laughter and applause.
The event was notable as the first time in U.S. history that two Roman Catholic candidates faced each other in a national political debate. Moderator Martha Raddatz, a correspondent for ABC News, pointed this out - and asked both men to discuss their faith and how it informed their positions on abortion.
"I don't see how a person can separate their personal life and their public life and their faith," Ryan said, adding that his reason also tells him life begins at conception. He recalled seeing an ultrasound of his 10-year-old daughter, Liza, at 7 weeks' gestation. "She was shaped like a bean and her heart was beating ... to this day we have nicknamed her 'Bean.'"
He argued that the Obama administration has been extreme in its support for abortion rights, such as requiring religious institutions to cover contraception for their employees. "Our church shouldn't have to sue the federal government" to perform its mission, Ryan said.
"I accept the church's judgment life begins at conception in my personal life," Biden said, "but I refuse to impose it on equally devout Christians, Muslims, and Jews. ... I don't believe I have the right to tell women they can't have control of their own bodies."
Common faith aside, Biden, 69, and Ryan, 42, represent different generations and two opposing views of the role of government in American life.
Biden espouses the traditional Democratic position that government should buttress the middle class and provide a safety net for the poor, while Ryan, the House budget chairman, is known as an intellectual leader of younger conservatives who hold to a libertarian view that limited government is best.
Some of their sharpest exchanges came over the future of Medicare. Ryan accused Biden of using scare tactics.
"He'll tell you about vouchers," Ryan said. "He'll say all these things to try and scare people. Here's what we're saying: give younger people, when they become Medicare-eligible, guaranteed coverage options that you can't be denied, including traditional Medicare. Choose your plan, and then Medicare subsidizes your premiums, not as much for the wealthy people; more coverage for middle-income people, and total out-of-pocket coverage for the poor and the sick. Choice and competition."
Biden retorted, "You know, I heard that death panel argument from Sarah Palin. . . . But let's talk about Medicare. What we did is, we saved $716 billion and put it back, applied it to Medicare. We cut the cost of Medicare. We stopped overpaying insurance companies, doctors and hospitals. The AMA supported what we did. AARP endorsed what we did. And it extends the life of Medicare to 2024."
Romney and Ryan "want to wipe this all out," the vice president said. "Their ideas are old and their ideas are bad, and they eliminate the guarantee of Medicare."
Usually the vice presidential undercards are afterthoughts in the greater campaign drama, but not always. In 2008, for instance, Palin faced the burden of convincing voters she would be up to the demands of the vice presidency; indeed, her debate with Biden drew more viewers than any of the three presidential debates that year.
For much different reasons, the stakes were also high Thursday. Polls suggest Obama's performance against Romney last week shook up the race, with states that had begun to lean Democratic, including Ohio and even Michigan, looking more competitive again. Democrats hoped Biden would undo some of the damage.
At one point, as they talked over each other on Medicare, Ryan quipped: "Mr. Vice President, I know you're under a lot of duress to make up for lost ground, but I think people would be better served if we don't keep interrupting each other." Biden laughed.
Contact Thomas Fitzgerald at 215-854-2718 or email@example.com, or follow @tomfitzgerald on Twitter. Read his blog, "The Big Tent," at www.phillynews.com/BigTent.