Stephen Moore: “Here is the biggest worry about an $18 trillion debt: What happens if/when interest rates start to drift back upward? Answer: This is the economic equivalent of the nuclear option. Each 1-percentage-point rise in interest rates causes the U.S. deficit to rise by more than $1 trillion over ten years. So a 300-basis-point rise in rates – nothing more than a return to normalcy –would mean about $5 trillion in federal deficits. If that happens, the debt-servicing costs grow astronomically and interest payments would become the biggest expense item in the budget. We start to pay more and more taxes just to finance past borrowing. This is what happened in Detroit; look at how that turned out.