According to comments by senior Treasury Department officials yesterday, the Senate's failure to raise the statutory national debt limit -- the House has done so -- threatens to constrain the nation's ability to meet its financing obligations. Treasury says the U.S. will reach its debt ceiling, currently $8.933 trillion, in early October. Because the Senate hasn't acted, Uncle Sam can't go to market for more money thereafter. This will force delays in Treasury's auction schedule, as well as run the risk of default on debt repayments -- which would be about as embarrassing as war declared on whimsy, i.e., unthinkable. Treasury estimates U.S. borrowing needs at $74 billion from October to December. It just needs Congress' permission to go to market.