By a 9-to-8 vote, the Senate Judiciary Committee yesterday killed a proposed constitutional amendment designed to push Congress toward a balanced budget.

Maryland Republican Charles McC. Mathias made the difference as he voted with eight Democrats to reject it against the six other Republicans and Democrats Dennis DeConcini (Ariz.) and Howell T. Heflin (Ala.) who supported it.

The amendment would have required the federal government to live within its income except during a state of declared war or when three-fifths of the members of both House and Senate approved deficit spending.

Supporters said Congress has proved -- by the fact that the budget has been balanced only once in 20 years -- that it is unable to discipline itself to hold down spending and that a constitutional amendment is necessary to get the budget in balance and push down crippling inflation.

Opponents argued that the new congressional budget process is working, that deficits have decreased substantially in the last three years and that a constitutional amendment putting control of fiscal policy in the hands of a 40 percent minority would be wrong.

Most members scrambled to get on record in favor of a balanced budget but said it should be achieved by having members stand up to be counted on specific issues.

Mathias said he has joined with Sen. Max Baucus (D-Mont.) in sponsoring a bill -- which can be passed and modified by majority vote of Congress -- to permit deficit spending only by a three-fifths vote of both houses of Congress. A constitutional amendment could be modified, if it turned out to be ineffective, only by a two-thirds vote of each body and approval by three-fourths of the state legislatures.

There will be opportunity for Congress to vote on spending restraints when the two budget resolutions come to the floor of each body. House leaders have promised a vote on the issue to Rep. James Jones (D-Okla.), who has proposed holding spending to a percentage of gross national product -- 21 percent the first year and 20 percent the next.

Jones, a member of the House Budget Committee, said that committee may adopt a spending limit of its own as part of the first budget resolution setting spending ceiling targets for next year, which should be before the House in about two weeks.

Sen. Birch Bayh (D-Ind.) acting Judiciary chairman in the absence of Sen. Edward M. Kennedy (D-Mass.), cautioned the committees against trying to incorporate economic theory into the Constitution. Mathias recalled the words of Chief Justice John Marshall that amending the Constitution is very serious business and sponsors should be sure their change would work.

Opponents of the amendment said they were convinced the proposed amendment wouldn't work, that government would find a way to change the bookkeeping to get around it.

Not all members were sure a balanced budget was much of a solution. Sen. Howard M. Metzenbaum (D-Ohio) said that most economists say balancing the budget would shave less than half a percentage point off inflation, which is running at an annual rate of 18 percent. And the spending cuts required to put the budget in balance would hurt those most in need of help, he said. Sen. Patrick J. Leahy (D-Vt.) called the budget amendment a "political gimmick" that would take several years to attach to the Constitution and put into effect.

But Sen. Alan K. Simpson (R-Wyo.) argued that members of Congress just can't bring themselves to make cuts required to balance the budget and that the only way to do it is "to shrivel the pie so we don't have so much pie to play with."

Supporters of the amendment, realizing they would lose after each member had made his speech, suggested putting together a package of both a constitutional amendment and a statutory approach. But opponents had the votes and rejected it. They then also rejected by the same 9-to-8 vote a request by Sen. Strom Thurmond (R-S.C.) that they send the constitutional amendment out to the floor anyway and let the Senate vote on it.