Johnny Isakson, a Republican from Georgia and always a gentleman, stood up to ask his question: “Do we need to act this year? Is it better to act quickly?”

“Absolutely,” Rogoff said. “Not acting moves the risk closer,” he explained, because every year of not acting adds another year of debt accumulation. “You have very few levers at this point,” he warned us.

…

Senator Kent Conrad, the chairman of the Senate Budget Comittee, said our current deficits were severe because we had very low revenues due to a slow economy combined with very high spending. He then offered his own stern warning to the assembled senators. Turning around in his chair in the middle of the room, he explained to his colleagues that when our high debt burden causes our economy to slow by 1 point of GDP, as Reinhart and Rogoff estimate, that doesn’t slow our economy by 1 percent by 25 to 33 percent when we are growing at only 3 to 4 GDP points a year.

Reinhart echoed Conrad’s point and explained that countries rarely pass the 90 percent debt-to-GDP tipping point precisely because it is dangerous to let that much debt accumulate. She said, “If it is not risky to hit the 90 percent threshold, we would expect a higher incidence.”

Senator and former governor Mike Johanns, a Republican from Nebraska, asked, “Is there a point at which the debt market rebels?”

“I don’t want to be fire and brimstone,” Rogoff said. “No one knows when this will happen. ” Yet, he added, “It takes more than two years to turn the ship around … Once you’ve waited too long, it’s hard to take radical steps.”