Paul Krugman writes that if the U.S. government doesn't raise the debt ceiling and goes into default,

it would be forced into savage spending cuts, around 4 percent of GDP, that wouldn’t just cause hardship (Surprise! No Social Security for you this month!) but amount to a severely contractionary fiscal policy, sending us into recession if it lasted any length of time. [Emphasis added.]

Why would S.S. checks not go out if the U.S. doesn’t raise the debt ceiling so that it can borrow more to pay its debts, unless the U.S. had to borrow the money sent out in S.S. checks?

Seems Krugman unwittingly parroted Obama inadvertently letting the cat out of the bag about Social Security being broke.