THE CENTRAL feature of the AWACS debate is not that so many senators have qualms about the deal. How could that be otherwise? Of course conscientious legislators have reservations about the wisdom of selling high-tech military hardware to a (currently) low-tech regime that not only is of uncertain staying power but also is in a state of war with a special American friend? It is hardly surprising that responsible senators asked if they were being called on simply to spare the president the embarrassment of defaulting on a sales commitment he might well not have made if it had not been pushed upon him by his predecessor and by careless aides. How could a Congress properly concerned with upholding its foreign policy responsibilities, after all, not wonder why the president was making such a tremendous investment of his and the country's prestige in a package on which there is is so much room for reasonable and honorable disagreement?

No, the central feature of the debate is not that roughly half the senators have qualms and that some 40 have managed to conquer theirs, with perhaps more to come before the vote scheduled in the Senate next Wednesday. No doubt those 40 have come to their views by different routes. Since we feel strongly that they are in the right place, however, we underscore what seems to have been the common core of their judgments. It is that of all the things that the United States must appear to be in the world, appearing serious is the first.

You can spend the day picking this and that flaw in the terms and the presentation of AWACS, but at the end of the day you still have to accept what the implications of a defeat would be. A victory may leave the president bleeding at home, but a defeat would leave him shipping water on the international high seas. He would look, to be blunt about it, sick --sick and weak. And there is no use saying, well, it's only the man, poor fellow, who has suffered. It is important for the management of American foreign policy that the president be seen as an effective leader, so the country will suffer, too.

An AWACS victory will not do all that needs to be done to establish the Reagan administration as a serious government. The deal will not actually be consummated in practical terms for years, and whether the equipment will then have any military value or will still be considered useful as a vehicle of American political influence is anyone's guess. Unquestionably, however, an AWACS victory will let the Reagan administration get on with other things, especially in the Middle East. A defeat raises the most troubling questions about whether the president can conduct foreign policy. A victory lets him try.

What will he then do? In this regard, we cite a telling point made last week by Sen. Robert C. Byrd (D-W. Va.), who, though anti-AWACS, is very far from being an instrument of the Israel lobby. The deal, he argued, fits into an administration effort "to establish a tacit regional consensus on meeting the Soviet threat among actors in the region whose primary focus is on the Arab-Israeli dispute." Mr. Byrd worries that the sale will freeze the Israelis. No less should one fear that the administration, in offering the package, asked and got nothing political for it from the Saudis.

Whether or not the sale would complicate an approach to Israeli-Palestinian peace, it would certainly make one more urgent. The proper way for Mr. Reagan to redeem the faith put in him by a pro- AWACS vote, if he gets it, is to move beyond a fascination with transfers and start grappling directly with the political conundrum at the heart of the instability of the Middle East.