As it stands, interest on the debt already accounts for almost $1 out of every $10 the government spends. If interest rates go up sharply, so will federal debt-service payments. Under current conditions, the Government Accountability Office already estimates that interest payments will account for 15 percent of all federal spending by 2035 and 27 percent by 2050 — and those numbers could be much higher if there are big increases in interest rates, which is a real possibility. But I should emphasize here that the GAO already forecasts that interest payments will grow to 27 percent of federal spending in just a few years — which would mean that we’d be spending more on interest payments than we spend on Social Security, which currently accounts for a larger share of federal spending than any other program. Put another way, the thing we will be spending the most on in the future is previous spending.

What is Washington going to do in that situation?

Washington could get its affairs in order with some combination of serious spending cuts, entitlement reforms, and tax increases. The problem with that is that there are three things Washington is determined not to do: cut spending, reform entitlements, and raise taxes. Fiscal crises have a way of bringing out the best in generally responsible governments: It was a left-wing government in Canada, not a conservative one, that responded to that country’s fiscal crisis in the 1990s with a conservative’s dream program: $10 in spending cuts for every $1 in higher taxes. But Canada is in many ways a more responsibly governed country than the United States is, and it has a less dysfunctional political culture.