THE VACUUM that is this administration's Mideast policy is hurting the president and the country alike. Into that vacuum, almost, it seems, in alternate weeks, pop the secretary of state and the secretary of defense, each cultivating a private departmental interest without even a pretense of sharing a common one. It is terrific political theater to see two Cabinet officers vying with each other for bureaucratic supremacy virtually in full public view. But it is a damaging comment on President Reagan's disinclination to accept the responsibility of his office and govern. And it is also, from the point of view of the national interest, absurd.

The latest episode of the Haig-Weinberger follies centers on the visit by the secretary of defense to Jordan, where he at least raised the question of selling King Hussein top-of-the-line aircraft and missiles to keep him from shopping in Moscow. By the time Secretary Weinberger's purpose and the various remarks and asides of his party had filtered back to Washington, the Israelis were invoking their own nightmare of American abandonment, and President Reagan was forced to step in and calm things down.

There seems to be a real personality clash between Mr. Weinberger, who distinguishes between the Israeli "people" and the Israeli "government," and Menachem Begin, who makes no secret of his intense distrust of the secretary. This is unfortunate, but it is not crucial. What is crucial in this episode is that Mr. Weinberger was flying his own kite, seeking to strengthen American links with friendly Arab states, evidently without regard to previous American assurances to Israel or to Secretary Haig's own recent diplomatic visitations. How can it possibly help the secretary of state to nudge along the Palestinian autonomy talks if at that very moment the secretary of defense is pleading with an Arab leader who spurns those talks to accept the favor of hot new American arms? Whatever his intent, Mr. Weinberger's effect was quite likely to bolster the Israeli hard line in ways that can lead to no good. Whether he will be appreciated in Arab quarters for having made the old college try or dismissed for not being able to deliver we don't know. But either way, how can it possibly help the secretary of state?

There is a sense, of course, in which not having a Mideast policy--a coordinated plan to pursue both diplomatic goals and security goals--is in itself a policy. The security side--the arms-selling, pact-making side--obviously has the strength under such conditions. To engage in this arms and pact business means closing ranks as much as possible with Arab states, demonstrating to them that the United States is loosening its special commitment to Israel, and accepting as natural and even desirable the inevitable consequent collisions with the Israelis. But this is an extraordinarily dangerous and reckless course, even a dishonorable one. Fortunately, there is an alternative, a very difficult one. It entails seeing the region as a whole, pursuing security interests firmly but with due respect to the sensitivities of all states of the region and accepting the political centrality of the need for Israeli-Palestinian coexistence. Right now, Mr. Reagan is over-engaged on the security side and inattentive on the political side. He is asking for trouble, and he is getting it.