THERE IS A SENSE in which almost everyone knows how to restore momentum to the search for peace in the Mideast, which is the purpose of the summit opening Tuesday at Camp David. Egypt must be satisfied, before it deals for itself on the Sinai, that down the road the Palestinians will win something of value on the West Bank. Israel must be satisfied that in yielding territory and control on the West Bank, it will not unduly endanger its security. The diplomats have a dozen formulas to get from here to there. The more sensible of those formulas hinge on setting up a controlled procedure over time so that, as the Israelis are assured the process is not getting out of hand, the Egyptians can feel (and claim) it is moving steadily toward an end.

Yet almost everyone knows, too, while there is scant hope of progress without an inventive formula, there is no guarantee of progress with one. That is merely a way of saying that the decisions to be made are political. That is, of course, precisely the rationale for a summit. Narrowly speaking, Camp David matches Israel's craving for direct Arab-Israeli talks with Egypt's desire for a direct American role and with the Carter administration's determination to set up a Mideast peace "framework." More broadly speaking, Camp David enables and enforces a degree of simultaneous political input into diplomacy that is available in no other context.

The summit taxes the three participating heads of government in heavy and very different ways.

On Israel's Menachem Begin the burden may well be the heaviest. Of the three, he alone must make what could be life-or-death decisions for his nation. In doing so, moreover, he will be called upon to review some of his own most profoundly held beliefs - his conviction that the West Bank is Israel's by biblical inheritance and that the right of Jewish settlement there cannot be abridged. In short, Mr. Begin must choose between spiritual passions and temporal imperatives. By the latter reference we mean the feeling of many Israelis, and many people elsewhere, that Israel's security hinges chiefly on compromise on the West Bank.

On Anwar Sadat of Egypt falls a not dissimilar requirement - to put national interest over national (or is it personal?) style. Egypt's interest clearly is to do what is necessary to reclaim its own territory and to get the Palestinian problem moving toward the compromise solution of a West Bank entity linked with Jordan. To do this, however, Mr. Sadat must demonstrate an empathy for Israel's anxieties, a steadiness of purpose and a degree of patience that have not always been in evidence since his marvelous trip to Jerusalem last November.

Jimmy Carter faces his own challenge. He must guide (and, when necessary, allow to maneuver on their own) two individualistic, idiosyncratic men, preventing each from succumbing to what surely will be the considerable temptations - as they hit the snags - to stop trying to succeed and to start trying simply to avoid the blame for failure. He must decide just how and when to play the "American card": to offer, as he almost certainly will, to become the guarantor for Israel of an Egyptian pledge to respect Israel's security needs, and the guarantor for Egypt of an Israeli pledge to withdraw to agreed frontiers and to allow Palestinians to move toward a home of their own. Uncertain as such a guarantor's role must be, it is almost impossible to imagine progress toward peace if the United States is not prepared to step into it.

It is imprudent to expect, let alone seek, a consummation of this process in this summit. An outcome considerably more tentative and ragged is far more likely - if you are, as we still tend to be, a relative optimist. Yet the summit offers an occasion where the quest for peace can be concentrated, and where each participant can give and get a sharper sense of what the real possibilities are. The first test of a successful summit will be whether they have genuinely agreed, at the end of it, that they can - and must - press on through hard bargaining to a sound and mutually acceptable conclusion.