The most serious question about President Reagan's remarks on the subject of nuclear weapons the other day, it seems to me, is whether he really believes what he said. It is more serious if he believes it, or did believe it when he said it on March 31.
One can speculate, I suppose, that he did not necessarily believe when he said it that the Soviet Union has ''a definite margin of superiority'' over the United States in strategic nuclear weapons, but that he felt he had to say something strong to defend his current military spending program against rising resistance in Congress.
It is customary in Washington for presidents, and for their political opponents, to overstate a case when arguing for or against some particular budget program.
A point has been reached where the consensus in Congress for a major increase in US weaponry is breaking down. It was one thing for Congress to vote for more guns when at the same time it was also voting for more kindnesses to the poor, for the working man (or woman), and for business and industry.
But it becomes a more difficult thing for a congressman to vote for more guns when at the same time he is being asked to cut back on school lunches and on benefits for the unemployed. When that happens he begins to look more skeptically at the proposals for more guns.
Congress is doing just that to the point that the Reagan military budget will be squeezed and trimmed substantially below the levels which Mr. Reagan encouraged a joyous Pentagon to propose. Even a loyal Republican, former President Gerald Ford, says it can be trimmed back safely.
So, if you choose to be optimistic about the competence of government in Washington you can assume that Mr. Reagan was only trying to put some stiffening behind his lagging military spending program when he credited the Soviets with more nuclear strength than they in fact have.
If that is the explanation, then Mr. Reagan has paid a price - and probably got little if anything in return. It is doubtful that the remark, particularly when it was contradicted at once by the experts, including the Senate's most respected hawk, Sen. Henry M. Jackson of Washington, will in fact save the military budget from heavy trims. In the meantime for a President to say it could encourage the Soviets to think that they are stronger than they really are. It can also frighten some of the allies into thinking that the US is no longer able to protect them.
It was a remark which, even had it been true, should never have been made by a president. His predecessors, both Democrat and Republican, have been careful to avoid saying any such thing.
Even more serious is the possibility that Mr. Reagan did not know when he made the remark that it was mistaken and that he still does not know it. Considering that it was unwise to have said it in the first place, it seems most likely that what he said was said in real belief. The implication is that the President of the US is not accurately informed about the facts upon which many a fateful decision may be made.
What a president believes to be the case about the nuclear weapons balance can be decisive in the budget programs he presents to the Congress, in the amount of taxes levied on the American people, on the funds to be cut from social programs in order to make more funds available for guns, on the calculations of foreign offices around the world and even on matters of war and peace.
Nothing is more important in Washington than that the President be accurately informed about such matters.
There is room for doubt arising out of this episode about how well the President is informed.
Accurate information about nuclear weapons is available inside the government. The State Department and CIA know the facts - and know there is no ''definite margin of superiority'' on the Soviet side. The US has some 9,000 deliverable nuclear warheads against about 7,000 for the Soviets. The US also has qualitative superiority in several areas such as accuracy, survivability and , in nuclear submarines, superior ability both to keep the seas and to escape detection.
Is there some block which keeps the facts from reaching the President? Is his mind so set on this subject that he does not hear what he is being told? Are his advisers uninformed, or perhaps unwilling to push information which the President would rather not hear? Or, as we speculated at the beginning, was he just indulging in political exaggeration in pushing his defense program?
You and I cannot know the correct explanation. But here is another example of the sort of thing which is undermining confidence in the competence of the present team in Washington.