the death of the US ambassador to Libya, and top domestic issues including health care and tax policy on a combative evening in Kentucky.
Passionate and adamant, Biden was on a mission to reverse Republican nominee Mitt Romney's polling surge, following his clear victory over President Obama in their debate in Denver ahead of the November 6 election. That was not real Romney I debated: Obama
But his constant smirking, guffaws and eye-rolling on a split screen when the earnest Ryan, 42, gave his answers risked distracting the audience of millions of television viewers at home early in the debate.
In a combo photo, vice president Joe Biden and Republican vice presidential nominee Paul Ryan face off during the vice presidential debate at Centre College in Danville, Kentucky. AP Photo
Biden, 69, came under intense pressure from Ryan on the Obama administration's handling of the crisis sparked by the killing of the US ambassador to Libya, Chris Stevens, in Benghazi on September 11.
Republican vice presidential nominee Paul Ryan at Centre College, Danville. AP Photo
"We will find and bring to justice the men who did this. Whatever mistakes were made, will not be made again," a steely Biden vowed, and then swiftly went on offense, touting Obama's record on national security.
Biden highlighted Obama's honored promise to end the war in Iraq, his effort to bring troops home from Afghanistan by 2014 and his decision to make the operation to hunt and kill Osama bin Laden a top priority. Issues at stake in US election
"The president of the United States has led with a steady hand and clear vision. Governor Romney, the opposite," he charged.
Ryan, a 42-year-old Wisconsin congressman, replied with a fierce assault on Obama's foreign policy record, and complained that the US ambassador to Paris had a Marines detachment while Stevens, in restive Libya, did not.
"Look, if we're hit by terrorists, we're going to call it for what it is, a terrorist attack," Ryan said, hitting a Republican theme that Obama did not want to admit the truth for political reasons.
Ryan also charged that the death of Stevens was symptomatic of a wider problem, in Obama's foreign policy, which Republicans charge is purely based on an apologetic stance to US enemies abroad.
"What we're watching is the unraveling of the Obama foreign policy, which is making things more chaotic and us less safe," Ryan said.
Biden, with typical Irish-American blarney, replied: "With all due respect, that's a bunch of malarkey."
A combination picture showing the US vice president Joe Biden's reactions during his vice presidential debate at Centre College in Danville. AFP Photo
With Iran's nuclear drive casting a shadow over America's immediate foreign policy, Biden said that the Islamic Republic was still a "good way away" from getting an atomic bomb, and vowed it would never get there.
He also accused Romney and Ryan of talking tough on Iran in a way that endangered US security.
Vice President Joe Biden during the vice presidential debate in Danville. AP Photo
"Facts matter. All this loose talk about all they have to do is get to enrich uranium and they have a weapon. Not true. Not true," he said. Fact or fiction
"If we ever have to take action, unlike when we took office, we'll have the world behind us. And that matters. That matters," he said, drawing attention to the most stringent sanctions ever imposed on Iran by the president.
Ryan however claimed Obama had been asleep at the switch.
"Let's just look at this from the view of the Ayatollahs," he said.
"What do they see? They see this administration trying to water down sanctions in Congress for over two years. They're moving faster toward a nuclear weapon. They're spinning the centrifuges faster."
Obama also went on offense on Thursday, apparently prodded into action by a universally critical response to his clash with Romney in Denver.
"He's trying to go through an extreme makeover," Obama said of his rival on a campaign swing through Florida.
"After running for more than a year in which he called himself severely conservative, Mitt Romney's trying to convince you that he was severely kidding."
Obama's passionate attack fleshed out a new theme adopted by his campaign, namely that Romney, after running to the right to win the Republican nomination, is covering up hardcore conservative stands to woo moderates.
New polling adding to the impression that Romney's polling surge had lifted the Republican ticket into at least a tie less than a month before election day.
Rasmussen Reports had Obama up a single point in its national poll of those likely to vote on November 6, while Gallup had a similar margin but with Romney on top.
US vice president Joe Biden and Republican vice presidential candidate Paul Ryan depart the stage following their debate at the Norton Center at Centre College in Danville, Kentucky. AFP Photo
A flurry of state polls revealed the race was essentially a toss-up. Key quotations
An NBC/Wall Street Journal survey had Obama up six points in what may be the kingmaker state, Ohio, but two other surveys in the state said the race was within a single point.
Romney had narrow leads in other battlegrounds Colorado and Virginia, while Obama was up in another Virginia poll and led by one percent in Florida, while there were signs of a narrowing race in other key states.
Thursday's clash between Biden and Ryan served as a warm-up act for the final two bouts between Obama and Romney, in New York state on October 16 and in Florida on October 22.
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