The sobering question raised by the Reagan administration's Libya operation is how serious it was meant to be.

There is a case, for instance, that terrorism is a great menace and Muammar Qaddafi a great terrorist, and this was the way to swat it and him. But not even the officials responsible for the policy are making bold claims of success on this front. On the contrary, they are nervously weighing just how Qaddafi or free-lance killers acting in his stead might strike back.

There is also a case that baiting, swatting and humiliating Qaddafi was the best way to embolden the next dissident colonel to bump him off. Such thoughts circulated in parts of the administration, but they do not appear to have been the engine of policy. It would have been a very long shot.

What, then, did the administration have in mind? My sense is that the president, feeling the same rage and frustration that sweep many of us, simply yielded to it. He instructed his (on-this-issue) feuding secretaries of state and defense finally to agree. George Shultz's impatience was joined to Caspar Weinberger's caution. The result was a plan designed to go forward under the cover of both international law and American opinion.

Let me be a Pollyanna about the outcome: the immediate combat ends without too much more excitement, the administration says it's upheld free navigation and hung tough, the other Arabs calm down and Qaddafi responds with acts no bloodier than the area's savage norm. Life in the Middle East goes on: nasty, brutish and long. That lets the Libya operation be seen in something closer to its true dimensions: not as a disaster, certainly not as a triumph, but as something of an unnecessary distraction from pursuit of the principal American interests in the Middle East.

These interests have little to do with attacking Qaddafi, whose fate is best left to a falling oil market, Arab intrigue and public ennui. They center on reinforcing the region's moderates, who are threatened less by terrorism than by the upheaval incident to economic and political modernization. Taking on Qaddafi -- in a manner that gilds his martyr's status -- reinforces radicals. It works the wrong way.

Taking on Qaddafi, for instance, is not nearly as important as helping to firm up Hosni Mubarak, whose reasonable ways are under heavy pressure at home these days. People who should know better are writing him off. But he is surely the best available bulwark against the forces of reaction in Egypt, which for its size, strategic heft and treaty with Israel remains the key Arab country. Mubarak needs economic help, political company and American attention to the sagging Egypt-Israel peace.

Nor is taking on Qaddafi nearly as important as keeping up a good connection to the kings of Jordan and Saudi Arabia and their moderate like. These rulers don't expect the United States to perform a backflip: they accept, however grudgingly, the special American tie to Israel. They do ask, however, a responsible American approach to the Arab-Israeli conflict and good-faith dealings with them.

For the past few years the political people in this administration have left the Arab-Israeli dispute to the bureaucrats, who tried and failed. The meaning of this default has not really registered in Washington: a whole once- bright sun -- the possibility of an Israeli-Jordanian opening -- may have set.

Sen. Charles Mathias is only the latest cold-eyed observer to return from the area alarmed by "the net loss of influence" the United States has suffered since its passage of successful diplomatic activism in the '70s. It flows not simply from American stinting on the search for peace but also from the administration's failure to go all out in Congress, against the Israel lobby, for arms sales to Jordan -- after, Mathias notes, "personal presidential pledges, six years of negotiations, and a quarter century of mutual effort to forge a cooperative relationship."

Nor is taking on Qaddafi nearly as important as bolstering Israel's Shimon Peres. Peres has ended Israel's political exposure in Lebanon and led a prodigious attack on inflation. By, I gather, licensing the military to zap the PLO from time to time, he made space to move toward negotiations with Jordan and some Palestinians. But negotiations did not materialize. The aloofness of Reagan and Shultz has to be a prime reason. With Peres now expected to leave the prime ministership in the fall, a fateful window closes.

Against all of this, the anti-Qaddafi operation is a diversion.