The budget debate is not least a foreign policy debate, and it is a more important one than the fight over MX or AWACS or anything else that's come along in the Reagan presidency. Its significance is the opportunity it affords Reagan to get in closer touch with the real world.

In his formal statements, Reagan put forward the right idea when he entered the White House. He said the first foundation of a strong foreign policy is a strong economy. But then he proceeded, with help from Congress, to dribble away his opening. Others, in his administration and in Congress, are trying now to recoup and hoping he will at least not block the way.

Some success in economic recovery is a long way off, if it comes at all. Just the appearance of an America attempting to correct course, however--notwithstanding that correction entails defense reductions--is on balance a tonic for American foreign policy. Politically, it suggests the United States is competent to play the leadership role that practically all nations, including adversaries, want and expect us to play. Economically, American recovery is the rising tide that lifts almost all other boats.

That improvement in the economy-- the world economy--would simplify the tasks before American foreign policy goes virtually without saying. Some people worry, however, that improvement would merely put in the president's hands the means for carrying out a questionable policy more energetically than he has been able to do so far.

I doubt it. Whatever Reagan's own proclivities, which should not be taken for granted, any recovery will also likely bring an altered balance of political forces in Washington. The pragmatic elements that have been working on economic policy will, if they succeed, have a more influential hand on foreign policy, too.

On the domestic side as on the foreign, and even among those sometimes regarded as doctrinaire Reaganites, there are enough sensible, prudently alarmed people to make a difference. George Shultz, who bestrides both policy realms, is the key man, though he could not possibly act without the implicit and explicit partnership of others in the executive branch and in Congress.

There is a hidden assumption here: that the pragmatic way is better than a crusade. Reagan campaigned against this assumption, saying in effect that the Soviet Union is not a normally pushy member of the familiar state system but a uniquely dangerous maverick dedicated to repudiating that system and substituting its own hegemony. Whether or how this assertion is true is a fair question. It seems to me beyond question, however, that fewer Americans would accept it as a basis for policy today than two years ago. The popular, party and bureaucratic support for the ideological commitment Reagan brought to the White House has shrunk.

The two big Soviet-American missile negotiations, INF and START, offer the right occasion for adjustment--on both sides. The numbers can be juggled. What matters more is that the administration state a position that reflects a strategic logic and that reasonable people regard as fair. Reagan has seemed to want a virtually flawless agreement--one that is invulnerable to the sort of attack he directed at SALT II and that erases what he and, now, not too many others believe to be an American power deficit. It would be better to regard an agreement as an imperfect transitional arrangement maintaining an existing rough parity but lowering the level of mutual risk and cost.

As it happens, a telling blow has just been struck at the contention--that the Soviet Union is an economic basket case and can no longer keep pace in arms competition--by which the administration has justified its strategic approach. The Soviet economy has slowed down markedly, but it won't collapse, and it gives every sign of continuing to increase defense spending 4 or 5 percent a year, says the CIA. People who had wondered about the integrity of the intelligence product should be reassured, for the new CIA analysis gives a powerful boost to the cause of moderation.

Even Yuri Andropov has a timely contribution. The new Kremlin leader has generated in Washington a sense of renewed Soviet diplomatic activism. Thus he has given valuable ammunition to policy-makers who feel that rather than hanging tough indefinitely and waiting for Moscow to falter, the United States should be moving out with all deliberate speed, meeting the Soviet competition and trying to make the deals that its strength warrants and its security requires.