President Bush’s first threat of a veto, on the transportation bill, looked serious enough for House Speaker J. Dennis Hastert to pass an extension on the current funding to give the House time to develop a smaller bill. Joint Chiefs of Staff Chairman Richard Myers last week warned Congress to prepare for a $4 billion military shortfall from operations in Iraq.

After years of expanding the deficit, the White House seems concerned about it now, a perfect time to apply pay-as-you-go budgeting to the entire budget resolutions, tax cuts included, for several years. Unfortunately, congressional Republicans have yet to seem concerned enough for that.

Not all Republicans. Four in the Senate – Maine Sens. Susan Collins and Olympia Snowe, John McCain of Arizona and Lincoln Chafee of Rhode Island – support “paygo” on the entire budget, with the latter two backing paygo’s five-year duration in an amendment by Sen. Russ Feingold of Wisconsin. Generally, the majority party supports paygo – which requires offsets for new budget costs unless three-fifths of each house vote to override the rule – only for entitlements but not for tax cuts.

The votes of these four are crucial to adding fiscal discipline to the budget process and would return a bipartisan restraint used successfully in the 1990s, helping to strengthen the economy and produce budget surpluses by the end of the decade. The debate now is whether Congress will keep the comprehensive Senate version in the budget resolution or accept legislation from the House Budget Committee that limits paygo to spending increases in the mandatory programs. That would make tax cuts scheduled to end in the next few years much easier to renew, to the detriment of the deficit.

Some of the cuts are likely to be renewed no matter what the hurdle: the marriage-tax penalty, the 10 percent income-tax bracket and the child-tax credit. Others, such as reducing the top income-tax rate and eliminating the estate tax, might not pass by nearly that much. Were Congress to advance these tax breaks for the wealthy by simple majority, it would have to cut programs or raise other taxes under the Senate’s version of paygo rules. It would demand that Congress examine how much those breaks were worth not only to those who would like them but in programs forgone.

One of the compromises being offered would impose the comprehensive paygo for one year only, but this is inadequate because the tough votes on taxes aren’t likely to arise until after that time.

A compromise of three or four years would be worth considering, however.

The nation has large infrastructure demands and it has a very serious demand for funding in Iraq. These are responsibilities that should be met, but doing so responsibly means doing without other spending. Paygo is an effective way to keep spending in line, and Maine’s senators should stick with their position on a comprehensive rule.