The change in the Kremlin upstaged Egyptian President Hosni Mubarak on his trip to Washington. Yet he deserved, and deserves, a respectful hearing. Egypt remains the most important country in the Arab world, the strongest influence for stability and calm, and the model for other Arab countries in dealing with Israel. Mr. Mubarak's sincerity in tackling Egypt's formidable problems is beyond question.

His special effort here was to break the stalemate on the Israeli-Palestinian dispute. To this end he tried to draw the Reagan administration to support the tentative peace gestures made recently by Jordan and the PLO. The Egyptian argument is that the United States can best moderate the PLO by opening a "dialogue" and thereby giving it the confidence to make the necessary further changes toward Israel. The Reagan administration, however, not only has a commitment to Israel not to open a dialogue until the PLO recognizes the Jewish state; it also believes it can best moderate the PLO by continuing to make plain that the PLO has no choice but to deal directly with the Israelis.

President Reagan and Secretary of State Shultz were badly burned by earlier Mideast initiatives. Everyone can see that Israel is still digesting the almost indigestible challenges of withdrawing from Lebanon and coping with economic crisis. Whether Jordan's and the PLO's gestures are conciliatory, rather than simply devious, is something the two of them have yet to establish. So the administration has some reason to hang back from the activist role -- activism, eventually, means pressuring Israel -- that Mr. Mubarak would cast it in. But it also has to be sure it does not make a habit or a virtue in itself of playing hard to get.

Meanwhile, Egypt's economic requirements remain urgent. President Mubarak asks for aid increases that, along with those sought by Israel, severely tax the American aid budget. Both sets of requests have to be considered in terms of the American interest. Regrettably, some pro-Israeli enthusiasts in Congress demand that Egypt's requests be considered in terms of a presumed Israeli interest: They would tie aid to Cairo to Egypt's return of its long-absent ambassador to Tel Aviv.

The issue of the ambassador cannot and should not be removed from its true context of Israel's and Egypt's deep and deeply troubling mutual disappointment since Camp David. It would be an abuse, moreover, to tie American economic aid to a needy second country to a fine point in its relations with a third.