Senator Rand Paul of Kentucky, a Republican supported by Tea Party activists, said Obama should "tell the country we will not default" even if the limit isn't raised. "Look, they can't be trusted with your money up here," he said May 12 on Fox Business Network. "They can't account for what you've given them, so by no means give them any more money."

The real action is occurring in the middle, where many Republicans and Democrats regard a debt-limit increase as necessary though unpleasant.

Senator Claire McCaskill of Missouri, a Democrat up for re- election next year, said she regrets her 2007 vote against raising the debt ceiling from $9 trillion to $9.8 trillion.

'Probably a Mistake'

"It was probably a mistake when I did that, but I was trying to send a message to my caucus that I wanted us to start paying closer attention to the spending," McCaskill said. "It's probably a vote that you shouldn't message with."

Even when your party holds the presidency, backing a boost in the debt ceiling is "a challenge," said Republican Representative Tom Cole of Oklahoma. "But if you're comfortable with what the spending's been for, I think that makes it easier."

Cole backed raising the limit during former President George W. Bush's tenure in part, he said, because he supported the wars and tax cuts that were running up the deficit.

"One of the challenges here from the Republican side is most of this recent spending we didn't vote for," including the 2009 economic stimulus measure, the health-care overhaul and most of the appropriations bills since Obama took office, Cole said. "It's a free vote when you're in the minority."

Since 1917

There has been a statutory limit on the national debt since 1917, when Congress passed the Second Liberty Bond Act to finance World War I, according to a report by the Congressional Research Service. Congress has voted to raise the ceiling 10 times since 2001, the report said.

Some lawmakers say their view on the debt limit has evolved with age and experience. Democratic Senator Tom Harkin of Iowa said that in his early years in Congress during Jimmy Carter's presidency he often opposed raising the borrowing limit because of his concern about the debt.