Vice President Biden and Rep. Paul Ryan (Wis.) tangled fiercely and noisily here Thursday night over the economy and foreign policy in a spirited debate that underscored the vast differences between the Democratic and Republican tickets on virtually every issue in the presidential campaign.

In sharp contrast to last week’s exchange between President Obama and Republican challenger Mitt Romney, the vice-presidential candidates clashed repeatedly during their 90-minute encounter. They differed over how to create jobs, whose taxes should and should not be cut or increased, how best to ensure the solvency of Medicare and Social Security, and whether the Obama administration’s foreign policy in the Middle East and Afghanistan is working.

The other contrast with the presidential debate was the absence of a clear winner. Romney was universally judged to have bested Obama in Denver, but Biden and Ryan each made their points with force and conviction. With the race tighter than it was two weeks ago, Thursday’s debate is not likely to result in a significant shift toward either Obama or Romney but is likely to raise the stakes when the two meet next week for their second forum.

Biden tried to dominate the debate and was a far more vigorous presence than the president last week. But he may have hurt his case by smiling sarcastically as Ryan made some of his points and interrupting repeatedly as the Wisconsin congressman defended his and Romney’s policies.

Biden repeatedly portrayed himself and Obama as protectors of the middle class while Ryan argued that the policies that he and Romney are advocating would do far more than the Obama administration would do to boost economic growth and help families whose incomes have flattened or declined in the past four years.

Biden attacked Romney for his recent characterization of the 47 percent of Americans who pay no federal income taxes as people who consider themselves victims, arguing that it showed an insensitivity to the kinds of people he grew up with in Pennsylvania.

“I’ve had it up to here with this notion, that 47 percent,” he said. “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.’ ”

At one point, he looked into a camera and said, “Look, folks. Use your common sense. Who do you trust?”

But Ryan argued that the administration’s policies have failed many of those same people. He noted that the unemployment rate in Biden’s home town of Scranton, Pa., is higher today than it was when Obama entered office.

“Look, did they come in and inherit a tough situation? Absolutely,” Ryan said. “But we’re going in the wrong direction. Look at where we are. The economy is barely limping along. It’s growing at 1.3 percent. That’s slower than it grew last year, and last year was slower than the year before. Job growth in September was slower than it was in August, and August was slower than it was in July.”

On foreign policy, Ryan cited the Sept. 11 killing of J. Christopher Stevens, the U.S. ambassador to Libya, and three other Americans as evidence that Obama’s foreign policy is “unraveling before our eyes” and said the administration has sent mixed signals on Iran. On the Middle East and Afghanistan, Biden defended the administration’s record, pledged that U.S. troops will leave Afghanistan by 2014, and accused Romney of being wrong on a series of foreign policy and national security issues.

Vice-presidential debates often are sideshows to the main campaign, but Thursday’s forum took on added significance after last week’s presidential exchange. Even before Denver, the race was tightening, especially in national polls. Most of the surveys released in the days before the first debate showed the race within the margin of error, although most of them still showed Obama in the lead. Since Denver, national polls have shown additional movement toward Romney, with the GOP nominee now a point or so ahead of Obama in many surveys.

The picture in the battleground states, where the election will be decided, is somewhat different. Like the national polls, a number of key states have moved in Romney’s direction. In many of those surveys, the movements are within the margin of error.

In Ohio, perhaps the most closely watched of all the battlegrounds, Obama continues to hold a narrow lead in a new NBC-Wall Street Journal-Marist poll and a CNN survey. Some other Ohio polls show the race a virtual dead heat there.

Thursday’s debate was more significant because of the standing of both participants. As vice president, Biden is accountable for the Obama administration’s record — a key target of attack by Ryan throughout the exchange.

Ryan, meanwhile, came into the forum as the architect of the House Republican budget blueprint and acknowledged as the intellectual leader of the new Republican Party. Ryan and his budget came under direct attack from Obama in spring 2011, at a time when Obama was saying little about Romney.

The debate was sponsored by the Commission on Presidential Debates and held at Centre College in Danville. ABC News’s Martha Raddatz served as moderator and pressed the candidates repeatedly to clarify their positions during each segment.

Biden lashed out at Ryan, whose budget proposal would overhaul Medicare and Social Security, over the broad entitlement reforms that Romney and Ryan have proposed.

Biden said the GOP Medicare plan, which would provide seniors a fixed amount of money to either buy into the government program or obtain private health insurance, amounted to a “voucher program” that he said would raise costs for future seniors. The vice president implored voters watching at home to make a gut decision about which party they trust to protect their Medicare benefits.

“Folks, follow your instincts on this one,” Biden said. Later, he added, “To cut the benefits for people without taking other action you could do to make it work is absolutely the wrong way. Look, these guys haven’t been big on Medicare from the beginning. . . . And they’ve always been about Social Security, as little as you can do. Look, folks, use your common sense. Who do you trust on this? A man who introduced a bill that would raise it $6,400 a year, knowing it and passing it, and Romney saying he’d sign it? Or me and the president?”

Ryan countered by charging that the Obama administration had been “caught with their hands in the cookie jar” by cutting $716 billion in Medicare funding in Obama’s health-care law. And Ryan said the Democrats do not have a “credible solution” that would stabilize the costly entitlement program for the future.

“He’ll say all these things to try and scare people,” Ryan said. “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.”

When Ryan attacked the administration’s 2009 stimulus plan, which included $90 billion for green energy projects, Biden interrupted and said that Ryan actually sent two letters to Biden’s office requesting stimulus money to help businesses in Wisconsin.

“I love that,” the vice president said. “This was such a bad program and he writes me a letter saying . . . ‘The reason we need this stimulus, it will create growth and jobs.’ His words. And now he’s sitting here looking at me.”

Ryan said that “we advocated for constituents who were applying for grants. That’s what we do.”

After Biden invoked Romney’s “47 percent” comments, Ryan rushed to his running mate’s defense. “They keep misquoting him, but let me tell you about the Mitt Romney I know,” he said.

Ryan recalled how Romney once helped a struggling family in his church pay for their children’s college education after the family was in a car accident, leaving the father paralyzed.

“Mitt Romney’s a good man. He cares about 100 percent of Americans in this country. . . . We want everybody to succeed. We want to get people out of poverty, in the middle class, onto a life of self-sufficiency. We believe in opportunity and upward mobility. That’s what we’re going to push for in a Romney administration.”

Biden said he did not doubt Romney’s generosity to some people, but he blamed the economic recession on GOP policies and cast the Republican running mates as cheerleaders for the country’s economic decline.

“We’re told everything’s going bad,” Biden said. “There are 5.2 million new jobs, private-sector jobs. We need more, but 5.2 million — if they’d get out of the way, if they’d get out of the way and let us pass the tax cut for the middle class, make it permanent, if they get out of the way and pass the jobs bill.”

Biden added, “Stop talking about how you care about people. Show me something. Show me a policy. Show me a policy where you take responsibility.”

The foreign policy sections of the debate included a discussion of whether there had been an intelligence failure in Libya before the four Americans were killed there and whether the administration had an effective policy to prevent Iran from obtaining a nuclear weapon.

Ryan charged that the administration had resisted tougher sanctions and had to be prodded by Congress to push for them. Biden countered by saying that they are “the most crippling sanctions in the history of sanctions” and scoffed that the Republicans in Congress could have brought along Russia and others to agree to the terms.

On Afghanistan, Biden argued that the United States has achieved virtually all its goals and that the timetable for withdrawing troops is hard and fast. “We are leaving in 2014. Period,” he said. “And in the process, we’re going to be saving over the next 10 years another $800 billion.”

Ryan said he and Romney, too, favor ending U.S. involvement “as soon and safely as possible” but said they would not want to broadcast to the enemy a firm timetable and said they would give military commanders all they needed to complete the mission successfully.”

Noting the historic significance of two Catholic candidates sharing the debate stage, Raddatz asked each man about the role their religion plays in their policy views on abortion.

Ryan said he opposes abortion in part because of his Catholic faith, but also because of “reason and science.” He said a Romney administration would oppose abortion with exceptions for rape, incest and to save the life of the mother. “I don’t see how a person can separate their public life from their private life or from their faith,” Ryan said.

Biden said he opposes abortion in his personal life, but said he does not believe the government should make such restrictions on citizens. “I refuse to impose it on equally devout Christians and Muslims and Jews, and I just refuse to impose that on others, unlike my friend here, the congressman,” he said. “I do not believe that we have a right to tell other people that — women they can’t control their body. It’s a decision between them and their doctor.”