So you thought Standard & Poor's decision to downgrade the U.S. credit rating had to do with unsustainable deficit spending and the recklessness of Congress in taking the nation to the brink of default before raising the debt ceiling?

Think again.

In a conference call Thursday discussing the need to reform the way credit rating agencies get assigned and paid to grade certain kinds of assets, Minnesota Sen. Al Franken suggested that S&P's downgrade could have been payback for an amendment he offered to the banking regulation overhaul.

Franken's amendment could establish a committee to assign credit rating agencies to review some of the riskier products of investment banks, like those mortgage-backed securities that helped caused the recession. Investment banks essentially bought superb ratings for those often worthless securities by hiring and paying rating agencies big bucks to tell investors what the banks wanted them to hear, Franken charged.

Franken modestly proposed that his amendment, which is being studied and has yet to be implemented, might have ticked off Stand & Poor's enough that the rating agency punished the Treasury Department, the Securities and Exchange Commission (SEC) and the entire U.S. financial system with a downgrade that set off huge losses in the stock market.

"I don't want to be conspiratorial at all," Franken said, "but you could, someone could, make a case that S&P is saying to the Treasury and SEC: 'If you implement the Franken amendment, watch out.' So I think there might have been a relationship in that way."