A snap CNN-ORC International poll showed voters who watched the debate narrowly favored Ryan over Biden by 48%-44%, a statistically even result after Romney scored a clear victory over Obama last week in their first of three debates.

Martha Raddatz of ABC News aggressively moderated the debate, challenging both candidates on some claims and moving on to various topics covering both domestic and foreign policy.

Ryan repeatedly said the Obama administration has taken the nation in the wrong direction, asserting it has hindered economic recovery and weakened U.S. influence around the world.

"The choice is clear: a stagnant economy that promotes more government dependency or a dynamic, growing economy that promotes opportunity and jobs," Ryan said. "Mitt Romney and I will not duck the tough issues, and we will not blame others for the next four years."

Biden called several of Ryan's remarks "malarkey" and challenged Americans to trust their common sense when judging proposals by the Republican challengers.

The tax and entitlement reforms proposed by Romney and Ryan would harm the middle class and favor the wealthy, Biden said in seeking to depict Republicans as protectors of the privileged.

"You think these guys are going to go out there and cut those loopholes?" Biden asked about unspecified moves promised by Romney and Ryan to balance broad tax cuts they propose.

On the topic of reforming the Medicare program for senior citizens, which Romney and Ryan seek to partially privatize, Biden referred to a Ryan proposal to provide partial government payment for seniors in the future to buy private health care.

"Folks, use your common sense. Who do you trust on this?" Biden asked, saying Ryan's plan would increase Medicare costs to recipients by $6,000 a year. Ryan disputed the claim, which was based on a proposal that he has since altered.

The debate pitted Biden, 69, and his almost four decades of experience in national politics against the 42-year-old Ryan, a 14-year congressional veteran.

Privately, senior Democrats told CNN they believed a strong showing by Biden could help the Democratic ticket, but wouldn't be enough to erase problems created by Obama's self-admitted bad debate performance against Romney.

Obama and Romney will square off again Tuesday in New York and October 22 in Florida.

Polling after the first presidential debate showed Romney tightening the race nationally and in some of the nine battleground states considered vital to either candidate's chances of garnering the 270 electoral votes needed to win the White House.

"I do think Joe Biden did his boss a lot of good tonight," CNN Senior Political Analyst David Gergen said after Thursday's debate. CNN Chief Political Analyst Gloria Borger said Biden's job "was to right the ship, and he did it."

Both analysts criticized Biden for his tendency to smile and roll his eyes in response to some of Ryan's comments, especially early in the debate, with Gergen saying Ryan won on style but the debate was even with regard to substance.

Biden also was more aggressive in his demeanor, repeatedly cutting off Ryan and sometimes talking at the same time as his rival to challenge specific comments.

At one point, Ryan told Biden that "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 responded: "Well, don't take all the four minutes then" in reference to how much time the candidates had to respond to a particular question. Overall, Biden spoke for about a minute more than Ryan during the 90-minute-debate at Centre College in Danville, Kentucky.

Ryan repeatedly sought to focus the debate on the Obama-Biden record of the last four years, arguing the administration's policies hindered economic recovery and weakened the nation's standing and influence in the world.

For his part, Biden tried to frame the election as a choice between differing directions for the country by contending policies of the Romney-Ryan ticket would hurt the middle class and move the nation backward on social issues such as gay rights and abortion.

Unlike Obama last week, Biden made sure to mention Romney's controversial comments secretly recorded at a May fundraiser in which the former Massachusetts governor spoke dismissively of 47% of Americans who he said depend on government benefits and don't pay taxes.

In one of his most effective moments, he gave a passionate defense of Americans who participate in the social safety net of entitlement programs and other benefits.

"These people are my mom and dad -- the people I grew up with, my neighbors." Biden said. "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.'"

In the biggest laugh line of the night, Ryan conceded Romney didn't express the thought exactly as he wanted at the fundraiser, then needled the gaffe-prone Biden by saying: "I think the vice president very well knows that sometimes the words don't come out of your mouth the right way."

Biden immediately responded "but I always say what I mean."