"The bond market is a place where everything is OK until it's not," Zandi says. "One day, everything seems fine and then there's a catalyst, and that's what's going to happen here. If [a rating downgrade] were to happen, it would shake the entire global financial system. It would go right to the bedrock."
That's why experts are still optimistic that Congress can avoid the "nuclear option" of default and pull together a clear and comprehensive plan to raise the debt ceiling and ultimately reduce public debt. "It would be ideal if we had over the next year a 10- to 15-year plan that really started to put our fiscal house in order that was deliverable," Swonk says. "That is what bond markets would welcome more than anything. A real concrete plan that has triggers in it and has some teeth."