PRESIDENT SADAT'S scheduled visit recalls Jimmy Carter's finest hour -- his personal patronage of the Egyptian-Israeli peace treaty. But the Egyptian stateman's trip to Washington also poses a problem for President Carter: the personal stamp he put on Camp David made it unavoidable that he would be held personally accountable when the Camp David process began to slow. The Middle East and the rest of the world are watching, and the American public -- and electorate -- are watching especially intently.

The Camp David process has slowed, predictably, at the threshold of the Palestinian question. Mr. Sadat's bold calculation in signing the peace treaty was that by providing the Israelis with evidence that their security would be strengthened through partnership with Arabs on one flank, he could help bring the Israelis to test the same policy on their other flank. He was under no illusions that Menachem Begin would be an easy case. But he perceived in Mr. Begin some of his own boldness and readiness to take chances, and he calculated that the prestige and political strength that would accrue to Mr. Begin as a peace-maker, plus the lesson of reassurance that the Israelis would learn from their peace treaty with Egypt, might melt Israeli resistance to the Palestinians in good time. Furthermore, Mr. Sadat counted on the American president to keep applying the special brand of persuasion and pressure, alternately hard-headed and prayerful, that had made Camp David a success.

Everybody knows what has happened since then. President Sadat, at heavy cost to his relations with other Arabs, has done essentially what he promised to do in matters falling between Egypt and Israel. He has also tried to demonstrate that Camp David holds a more fruitful answer to the Palestinian question than any available alternative. Mr. Begin, meanwhile, has interpreted the narrow and particular language on the Palestinians in ways reflecting his own and his constituency's hostility to independent and self-respecting Palestinian evolution. The result is an impasse in the Egyptian-Israeli talks on Palestinian autonomy. What Mr. Carter will discover, as he receives Mr. Sadat this week and Mr. Begin next, is whether this is a temporary impasse, reflecting both the Egyptian's and the Israeli's now-confirmed bargaining tactic of reserving their important concessions for Jimmy Carter, or whether it is the profound, unbreakable impasse that Camp David critics have anticipated from the start.

For many of those critics, whether they are Arab opponents and doubters or the State Department's Arabists, the time for bargaining is over. The two groups merged their frustrations in the recent United Nations resolution, which described as "Palestinian" territory both the West Bank (whose status Camp David left open to negotiation) and Jerusalem (whose status Camp David wisely determined to be too contentious to touch at that time). If all this is determined to be Palestinian even before negotiation, of course, then the only purpose of negotiation is to set the terms for turning it over. Mr. Carter subsequently disavowed the resolution, but Secretary of State Cyrus Vance then perversely re-avowed it, thus darkening the cloud the initial American approval had cast over the runup to the May 26 "target date" for completion of the autonomy talks.

Mr. Sadat, at any rate, seems almost uncannily serene. Mr. Begin must answer for the immense obstacle his West Bank settlements have put in the path of the autonomy talks, but the Egyptian president has nothing of that nature to answer for at all. In the year since the peace treaty was signed, he has seen the beginnings of some of the economic benefits that he hoped peace would bring to Egypt -- presumably, he will be nudging President Carter again on this score. He has also seen an even more rapid and conspicuous development of military ties with the United States. Egypt is clearly winning its quiet but intense competition with Israel to become the chief regional strategic partner of the United States. This is a compensation of sorts for disappointment on the political level, and it carries its own risks, but it is something important to President Sadat all the same. He will be a welcome and honored guest in Washington. The very least all Americans should have learned -- including those with misgivings about his policy or his style -- is not to sell his short.