U.S. Vice President Joe Biden and Republican vice presidential candidate U.S. Rep. Paul Ryan (R-WI) participate in the vice presidential debate as moderator Martha Raddatz looks on at Centre College October 11, 2012 in Danville, Kentucky. (Win McNamee/Getty Images)
DANVILLE, Ky. -- Republican Paul Ryan said there aren't enough rich Americans to tax to pay for all of President Barack Obama's spending.
Ryan told viewers of the vice presidential debate, quote, "Watch out, middle class. The tax bill is coming to you."
Ryan said he and Mitt Romney want to give Congress a framework for taxes that involves lowering rates by 20 percent. He said the guarantees can be paid for by closing loopholes, mostly on the upper class. But he didn't saying which loopholes he'd close.
Vice President Joe Biden said the only way to pay for Romney's plan is to raise middle-class taxes, claiming Republicans insist on needless tax cuts for the rich and are holding hostage middle-class tax cuts that Obama wants to make permanent.
Vice President Biden and congressman Ryan clashed over their plans for Medicare and Social Security, government programs for seniors.
Often appearing exasperated by Ryan, Biden said he and President Obama would never sign onto the sort of voucher program proposed by Ryan and GOP presidential hopeful Mitt Romney. Ryan fired back that the Republican plan would give seniors more choice in their medical care.
Romney's plan would introduce subsidies to help future retirees buy private insurance or join a government plan modeled on traditional Medicare. Obama's health care law cuts Medicare spending for hospitals and other providers by more than $700 billion over a decade.
Biden said Republican Mitt Romney's opposition to the auto bailout and government steps to prevent foreclosures "shouldn't be surprising" given his comments about the 47 percent of Americans who don't pay income tax.
Biden was referring to remarks Romney made to wealthy donors. In a secretly recorded video, Romney said 47 percent of Americans believe they are victims and entitled to government help.
Biden said some of those people are senior citizens living off social security.
President Obama never mentioned Romney's comments in his first debate, to the dismay of many Democrats.
Romney has since said his comments were wrong. Biden said Thursday night if voters believe they were a mistake, he has "a bridge to sell you."
The two said their Catholic faith informs their public policy decisions, but they come down on different sides of the abortion debate.
Biden said his Catholicism teaches that life begins at conception but that he would not impose that belief on people of other faiths. Ryan said he opposes abortion but that the policy of a Romney administration would include exceptions in cases of rape, incest or when the life of the mother is at stake.
Biden claimed his administration has the toughest sanctions in history on Iran, even as his Republican rival said the White House has no credibility on the issue.
In the debate, Ryan said President Barack Obama has allowed Iran to get four years closer to building a nuclear weapon.
Biden said he is "quite confident" the administration could deal a serious blow to Iranian's nuclear ambitions.
The vice president called Ryan's criticisms of his foreign policy a "bunch of malarkey," but Ryan contended he would stand up for Israel.
On Libya, Ryan slammed the Obama administration for failing to call the attack on a U.S. consulate in Libya a terrorist attack.
For his part the vice president criticized Ryan and Mitt Romney for launching political attacks before they knew the facts on the ground.
Ryan said the U.S. is witnessing the unraveling of President Barack Obama's foreign policy. He said the attack that killed U.S. Ambassador Chris Stevens shows the U.S. is projecting weakness abroad.
Biden responded that's, quote, "a bunch of malarkey." He said the U.S. will bring those responsible to justice and ensure any mistakes aren't repeated.