Despite the sudden enthusiasm for legislation to force a gradual end to federal budget deficits, there is considerable skepticism over how the proposed measure would work and whether a future Congress will stick with an approach that may lose much of its current political attractiveness.

With this in mind, proponents of a constitutional amendment that would require a balanced federal budget said yesterday that they will continue to press for an amendment even as they support the pending Senate legislation, whose chief sponsors are Sens. Phil Gramm (R-Tex.) and Warren B. Rudman (R-N.H.), along with Ernest F. Hollings (D-S.C.).

Lewis K. Uhler, president of the National Tax Limitation Committee, a leading advocate of the constitutional amendment, called the Gramm-Rudman proposal "terrific," adding that it should "help lay the groundwork" for adoption of a constitutional amendment by demonstrating that "there is a process by which we can get to a balanced budget."

"It's a thoughtful, systematic approach to curbing the deficit, but that doesn't assure it will be implemented," Uhler said.

Mark W. Goodin, an aide to Sen. Strom Thurmond (R-S.C.), who is pushing the constitutional amendment in the Senate, said the Gramm-Rudman proposal did not lessen the need for the amendment. "The statutory approach has been tried before," Goodin said. "We hope this particular approach will work, but it has not been particularly effective in the past. Congress can come back and undo what it has done."

Congress could avoid the proposal's automatic cutbacks by approving an alternative plan, including spending cuts, tax increases or a combination.

One factor feeding skepticism about the proposal was the widespread recognition that the surge of support in the Senate, and the scramble by House Democrats to respond to the idea, reflects a political reality which could easily change. Returning from their August recess, members of Congress reported little voter enthusiasm for tax reform but growing concern over the deficit.

Alan Greenspan, a former chairman of the Council of Economic Advisers, said the Gramm-Rudman proposal would be workable only if it gave the president clear and unambiguous authority to slash spending. Congress may not want to grant that kind of authority.

The proposal would require that any cuts necessary to meet deficit targets come equally from discretionary spending, including defense, and from annual adjustments for benefit entitlement programs. But budget analysts noted yesterday that this may not be the way it works in practice.

The Senate proposal already exempts Social Security from cuts. In addition, Greenspan and others noted, interest payments on the national debt -- which together with Social Security account for about one-third of the federal budget -- would have to be made and Defense Department and other agencies' contracts would have to be honored. With so much spending excluded from cuts, the budget ax could fall heavily on programs that traditionally have enjoyed strong support in Congress.

In that event, support for the proposal could turn into equally strong sentiment to repeal it or exempt other programs.