Q. Why do we have a debt ceiling anyway?

A. Most countries don't. In 1917 Congress set the first debt limit as part of the effort to finance America's participation in World War I. The law allowed the U.S. government to sell bonds (acquire debt) without asking Congress to approve every bond offer but capped the amount the government could borrow. “It's kind of like a nuclear weapon,” said Powell, a former undersecretary in President George H.W. Bush's Treasury Department. Congress should instead use its legislative power to cut spending, he said.

Q. Can't the president just borrow what he needs under the powers of the 14th Amendment?

A. Obama, who is up for reelection next year, is unlikely to take that risky political path. The 14th Amendment does say the validity of the public debt shall not be questioned.

But Mann said borrowing more by using the 14th Amendment argument is likely to upset the financial markets anyway, leading to higher interest rates. And "the Republicans would probably try to impeach him. It would darken our politics rather than resolve them,” he said.

Q. What's next?

A. Although the debt ceiling won't be reached until Aug. 2, the fallout could start earlier. Credit agencies already have begun rethinking the United States' sterling credit rating, which allows the country to borrow money at low interest rates.

"There's a lot of nervousness in those markets," Mann said, noting higher interest rates could wreak havoc. "We have come through the greatest financial crisis since the Great Depression. It's a fragile world."

Obama has threatened to veto anything that raises the debt ceiling for only a short while, saying that will not assuage the financial markets.

"Now they're just looking for something that can get passed," Certner says.

Tamara Lytle is a freelance writer in the Washington, D.C., area who has covered government and politics for more than 20 years.