They invoke Alan Greenspan to argue that paying back any more debt would require buying Treasury bonds from their holders before they come due, a potentially costly step. There are, however, several flaws in the Bush numbers. If you are willing to allow the government to use some of its surplus to buy stocks and bonds that could be sold in 20 or 30 years to pay the baby boomers' bills, then there is no limit on how much money could be set aside today. The problem of paying off the debt is the only long-run challenge that is squarely addressed in Bush's budget blueprint. But it is the only long-run challenge that America can afford to delay addressing.
Budget forecasts are amazingly fickle.
We can wait five years to find out if there is a serious risk of paying off the debt. Another issue behind various SS proposals is whether SS should remain an essentially defined benefits plan or change to a defined contribution plan, or some mixture. Usually politicians don't bring up this issue and when it came up in the presidential debates it got ignored for the most part. One of GWB's planks was that his plan, such as it was stated, included the ability of workers to have an investment account separate from the federal IOU which SS now represents. Contributions to this separate account would be deductions from the SS contribution, and would reduce somehow the eventual federally obligated SS payout.