"The national debt is certainly a ticking time bomb. There's no question that if we don't do something about it, it's going to go off," says Robert Bixby, executive director of the Concord Coalition.
Bixby, like most economists, thinks there comes a point when the debt becomes unsustainable -- when interest payments on the debt alone create an economic implosion.
"We're spending about $200 billion on interest now. That’s much more than we're spending on operations in Afghanistan, more than we're spending on Medicaid," he said.