DANVILLE, Ky. -- In a battle of understudies, Vice President Joe Biden and Republican rival Paul Ryan went after each other repeatedly Thursday night on issues ranging from the fate of Medicare to the terrorist attack on U.S. diplomats in Libya.Both were assertive, eager to trumpet the strengths of their tickets and equally zealous in ripping the other party.Ryan was aggressive from the outset, challenging the Obama administration's first accounts of the Libya attacks, which claimed that an anti-Muslim video inflamed a crowd rather than calling it a terrorist attack. He noted that President Barack Obama referred to the video six times in a speech to the United Nations after the Libya attack."This is becoming more troubled by the day," Ryan said of the still-emerging details of what the administration knew in those first days after the attack. Ryan said it is "indicative of a broader problem ... the unraveling of the Obama foreign policy."Biden defended the administration's response, saying it relied on intelligence reports that turned out to be false. "We will get to the bottom of it," he said.Ryan, the fresh-faced congressman who had never debated on the national stage despite his 14 years in the House, betrayed no signs of nervousness about the showdown with Biden, a veteran of 36 years of Senate debates.Their meeting, televised nationally from Centre College, was moderated by Martha Raddatz of ABC. The candidates sat at a table, fielding domestic- and foreign-policy questions.The vice presidential debate is usually an afterthought with little impact on the race. But this, the only such meeting between the two, took on added significance after Obama's lackluster debate debut Oct. 3 against Mitt Romney.Romney takesthe lead in FloridaSince then, Romney has pulled even with Obama in national polls and closed the gap in several battleground states.In Florida, Romney opened up a 7-point lead, according to a new Tampa Bay Times/Bay News 9/ Miami Herald poll. Obama has a 1-point edge in an NBC/ Wall Street Journal/Marist poll of likely voters that was released Thursday. The margin was the same as before the Obama-Romney debate.In Ohio, Obama leads by 6 points. He had led by 8. And in Virginia, Obama was up 2, but Romney is now ahead by 1.With just one debate, Biden and Ryan bounced back and forth from domestic to foreign policy.Biden used a question about the unemployment rate to criticize taped comments in which Romney disparaged 47 percent of Americans as non-tax-paying freeloaders. Biden accused Romney of saying he'd let housing foreclosures hit bottom.In one of the more personal exchanges, Ryan told how Romney helped a family hit by injuries pay for college and how he gives more than 30 percent of his income to charity -- more than Biden and Ryan combined."Mitt Romney is a good man," Ryan said.Referring to the criticism of Romney over the "47 percent" comment, Ryan said, "He cares about 100 percent of the Americans."Noting Biden's own tendency for gaffes, Ryan joked that "sometimes the words don't come out of your mouth the right way."Biden, noting that his daughter and first wife were killed in a car accident four decades ago, said he understands the impact of tragedy. Of Romney, he said, "I don't doubt his personal commitment to individuals. But I know he had no commitment to the automobile industry."Romney opposed the government bailout of Chrysler and General Motors. Both automakers are now on firmer financial ground.Biden was animated throughout the debate, at turns smiling and laughing, as well as grimacing in response to Ryan's answers to Raddatz's questions. The vice president interrupted as Ryan criticized the administration's Middle East policy."That's a bunch of malarkey," Biden said, later suggesting that Ryan's remarks were "a bunch of stuff."When Raddatz gave him a quizzical look, Biden told her, "It's simply inaccurate."Ryan offered, "It's Irish."Both men are Irish Catholics.Split on IranThey tangled on Iran.Ryan said that Iran is "racing toward" developing nuclear weapons and that the administration dragged its feet in imposing sanctions that it now says are working to deter the regime."When Barack Obama was elected, they had enough nuclear material to make one bomb. Now they have enough for five," Ryan said.Biden accused Republicans of "bluster" and "loose talk" and asked Ryan what else could be done beyond the "most crippling sanctions in the history of sanctions." He asked whether Ryan was saying that he'd back war."How are they going to prevent war if there's nothing more they say we should do than we've already done?" Biden said. "We feel quite confident we could deal a serious blow to the Iranians."Heading into the debate, the two campaigns clashed repeatedly in ever tougher tones since the first presidential debate shook up the race.Most notably, Romney has appeared to stake out or emphasize more moderate parts of his agenda, and the Obama campaign has all but accused the rival ticket of lying to paper over the more conservative message that Romney used to win his party's nomination.Among the top issues, the campaigns disagree sharply on several fronts:On abortion, Romney caused a stir this week when he told The Des Moines Register that "no legislation with regards to abortion" would become part of his agenda. Romney has said he would sign legislation limiting abortion if it ever reached his desk, though he said in the 2008 campaign that that is unlikely anytime soon, given the division on the subject.He also has said he would sign an executive order to ban the use of U.S. foreign aid to pay for abortions overseas and would end federal aid to Planned Parenthood.Obama supports abortion rights without any restrictions.On Medicare, Obama wants to retain the traditional system, relying on the 2010 Patient Protection and Affordable Care Act to extend the life of the program by raising fees and shaving $716 billion from anticipated payments to healthcare providers.Romney vows to repeal Obama's healthcare act and would replace the system.Starting in 2023, he'd give people checks to buy Medicare or private insurance. He has said his plan is more efficient and allows seniors to make their own choices. Ryan had proposed a similar plan that would cap the amount of those government checks, or vouchers, but Romney would not cap them.
CNN's instant poll gave a 48-44 edge to Ryan. A CBS News poll of undecided voters favored Biden.