From MSNBC: "Standard & Poor's had warned that the nation's credit rating would be subject to a downgrade without a credible deficit-reduction package worth $4 trillion over 10 years. The package agreed to by congressional negotiators falls well short of that mark."
But there's also this: "Analysts said the main reasons for a downgrade include political confusion surrounding the process of hiking the debt limit and doubt that agreement would be reached on more deficit reductions."
That means that if the republicans didn't make a crisis out of the debt ceiling, the downgrade wouldn't have happened.
http://www.msnbc.msn.com/id/44040574/ns/business-stocks_and_economyThe ultimate point of all this is that republicans are more loyal to illegitimate "pledges" than the nation. They could have chosen to do what's best for the country. Instead they chose to prove their collection of ideas that they call an ideology is a failure.