In urging that Congress and the states enact a constitutional amendment for a line item veto, President Reagan is taking a position supported in one fashion or another by almost every president since Ulysses Grant. A line item veto would enable a president to delete individual parts of an appropriation bill rather than having to kill the entire bill, as is now the case. Such a veto would sharply expand the power of the White House vis-a-vis Congress. Federal funding for the states would also be subject to the line item veto.
For precisely these reasons, it is unlikely that Congress or the states will approve such a constitutional amendment in the near future. Besides, even if President Reagan had additional expenditure-curbing authority - as Mr. Reagan called for in his State of the Union message - the line item veto would not target most federal spending. In other words, a line item veto falls far short of being a practical solution to reducing current and future budget deficits that, according to the Congressional Budget Office, could reach $325 billion by the end of this decade if fiscal policies remain unchanged.
Over four-fifths of the budget would be protected from such a veto - including entitlement programs, defense spending, and interest on the national debt. Many entitlement programs cannot be substantially cut because of law. Other federal programs, like defense, are programs that Mr. Reagan would be loath to reduce.
A number of bills for a line item veto are before Congress. It is interesting to note, however, that the Republican-controlled Senate recently rejected two measures that would be somewhat similar to a line item veto, but would not require a constitutional amendment. Both measures, which would increase the authority of the president to rescind certain funds appropriated by Congress, were defeated.
What is really the job that needs to be done? Is it not fashioning a political consensus in Washington - and a national consensus on the part of the American people - to make broad and far-reaching structural changes in the federal budget? That means rethinking and rearranging the huge defense program now in place. It means rethinking and restructuring expensive entitlement programs, such as medicare.
Granted, a line item veto could serve as a goad to budget reform. Congress should consider that possibility. And, as Mr. Reagan correctly notes, governors in 43 states have variations of such a veto. Mr. Reagan skillfully used line item veto authority when he was governor of California. Many states, however, have a balanced budget requirement - which makes such a veto effective. The federal government, by contrast, must often borrow against the future, such as in the case of war or economic downturn, to prime the economy or bring about certain policy results.
The real challenge remains the deficit. Is it really impossible for the White House, Congress - and yes, the American people - to reach a national consensus on the deficits? Given hard bargaining and determination such a consensus need not be considered improbable.
In considering whether President Reagan and the Democrats are all that far apart on the need to reduce deficits, it might be noted that Democratic contender Walter Mondale has now come forth with a plan to reduce the federal deficit by ''more than half.'' Republicans, and some Democrats, maintain that the Mondale plan is vague and that the figures are questionable. The point that needs to be kept in mind, however, is that both President Reagan and former Vice-President Mondale are now looking at the budget numbers - seeking ways to reduce the deficit. So too are other Democratic contenders. That is step one in reaching a consensus.
One final thought seems warranted here: Just as a line item veto would be only a goad toward budget reductions, so turning to the recommendations in the Grace commission report on federal waste will not by itself reduce the deficit all that much. Many of the proposals are useful. But even Republican-oriented economists such as Rudolph Penner and Herbert Stein question whether the savings of $424 billion (in three years) could really be achieved. Indeed, Mr. Penner notes that possible savings listed in the report are based on an inflation rate double what is expected.
The task at hand regarding the deficits seems obvious: The White House and Congress must come together to reduce federal spending and raise taxes.