IHS Global Insight Chief Economist Nariman Behravesh said S&P has unrealistic demands because lawmakers are unlikely to agree to a major deficit reduction package until after next year's elections. "If they really think there is going to be a comprehensive solution before 2012, they are grossly mistaken," he said.

Where Beers sees ominous gridlock over the debt, Behravesh sees progress. "Think about where we were six months ago: We were talking about stimulus," he said. "The good news is U.S. politicians are talking" about trillion-dollar budget cuts.

He said S&P is "itching to pull the trigger" on a credit downgrade, saying "it's almost like they're overreacting in the other direction" in order "to make up for past errors."

Former Congressional Budget Office Director Doug Holtz- Eakin, who advised the 2010 Republican presidential campaign of John McCain, said S&P is right to question the political will in Congress to address the deficit because it's the central question surrounding the debt.

Political Wherewithal

"There is no question that the U.S. economy remains the largest, strongest on the globe and it has the financial wherewithal to pay its debts," he said. "The question is, is that financial wherewithal matched by political wherewithal? And that's what they're trying to find out."

Beers said critics of the company's record during the housing crisis "know nothing about our sovereign ratings, which have an excellent track record." He said it's impossible to assess a government's credit rating without making judgments about its politics.

"Economic policy is part of a political process," he said. "Every government has to make choices, and it has to do it in some political context, and we have to look at that and decide how plausible that is."

'Sheer Difficulty'

The gridlock over the debt limit "highlights the sheer difficulty" lawmakers are having coming to agreement, he said, which has prompted S&P to shorten the timeframe over which it wants to see major cuts. He is skeptical that next year's election will be "that decisive on this issue."

U.S. lawmakers are lagging behind other similarly rated governments that have also faced debt challenges, he said, pointing to countries such as Britain that are implementing plans to tighten budgets.