On the primary campaign trail, this is the season of promises. But the record $3.1 trillion federal budget sent by President Bush to Congress yesterday shows how the continuing war in Iraq and mounting Social Security and Medicare costs are going to make new promises difficult to keep.

Mr. Bush is proposing an overall spending increase of 6 percent that would produce a near-record $410 billion deficit for the federal budget year beginning in October. Much of the added money would go to pay for the ongoing wars in Iraq and Afghanistan as well as increases in Social Security and Medicare costs and a pending $145 billion economic recovery package.

Presidential candidates should do the math and explain to voters just how they intend to deal with the soaring cost of the war in Iraq and the struggle against terrorism elsewhere if they are proposing ambitious new federal programs.

New taxes, like those used by President Bill Clinton to cut the federal deficit in the 1990s, are not an attractive option with the nation facing a possible recession. And even an early withdrawal from Iraq is likely to be expensive in the short run, not to mention the growing costs of fighting terrorism abroad.

To pay the mounting costs of the wars, Mr. Bush plans to slash discretionary spending elsewhere, including the elimination of dozens of education programs and more than $800 million in energy assistance to the poor.

The challenge faced by the president's opponents is that a sizable Republican minority in the Senate is likely to successfully defend many of his priorities - especially his tax cuts - as it did recently by upholding his veto of increased federal heath care spending for children. Mr. Bush has demonstrated how difficult it would be to cut spending on the wars.

And if the economy fails to grow moderately, as predicted in Mr. Bush's budget calculations, members of both parties may well be ready to spend much more to help fuel a recovery.

To some economists, the rising deficit doesn't matter. They note that the debt amounts to a relatively low percentage of what has been a fast-growing economy. But others disagree, noting that the future is clouded by a weakening dollar, increasing debt abroad and commitments that will be difficult to abandon.

The expected wrangling in Congress over this budget is likely to carry on at least until the November election. The presidential candidates like to talk about change, but they also need to explain how they intend to put the government's financial house in order.