Debt

There's no such thing as reading the US Constitution too often. Check out Section 4 of the Fourteenth Amendment.

The validity of the public debt of the United States, authorized by law, including debts incurred for payment of pensions and bounties for services in suppressing insurrection or rebellion, shall not be questioned.

These are very strong words. It doesn't just say that the US must pay its debts, it says the US can't even hint that it might not pay its debts.

Now let's think about the Social Security "crisis." Currently, SS takes in signficantly more money than it pays out; it uses the surplus to buy US Treasury Bonds. Eventually, the aging of Baby Boomers will mean that SS will pay out more money than it takes in; the plan is to cash in those t-bills to pay for it. Projections show that this keeps SS solvent until about 2040 or 2050 --- and mind you, after that point, it isn't that the system is unable to pay any benefits, it's that that it can't pay all of the benefits promised with the current regime of retirement ages, cost-of-living adjustments, et cetera. We could still pay retirees more in real dollars than we pay now.

Ah, but when we go to redeem those t-bills, since there's a sense in which the US government owes that money to itself, couldn't the government just refuse to honor those t-bills in a fit of fiscal irresponsibility? Well, not without a constitutional amendment repealing Section 4 of Amendment XIV, it can't.

In fact, as DeLong points out, if an elected official suggests that those t-bill are no good, it violates their oath of office.