AS SECRETARY OF STATE George Shultz and Soviet Foreign Minister Eduard Shevardnadze prepare to meet this week, twin campaigns are being waged on an issue with a powerful, proven potential to affect superpower relations. In Moscow the Kremlin, having permitted a slight increase in Jewish emigration, is ostentatiously freeing some of the most prominent remaining "refuseniks." Elsewhere fighters for this cause are warning that the carefully timed release of a few celebrities is part of a broader campaign by Mikhail Gorbachev to buy trade and credit, and accommodation and de'tente, on thecheap.

Certainly Natan Shcharansky's powerful caution, printed on the opposite page today, is right on the subject of the current leadership's record: Leonid Brezhnev allowed 50 times more Jews to emigrate (in the single biggest year, 10 times more). He never enacted legislation nearly as restrictive in practice as the Gorbachev law -- touted as an advance -- limiting emigration to those with a spouse, parent, sibling or child already abroad. The Gorbachev emigration rules, moreover, make very arbitrary use of an applicant's past knowledge of official secrets to deny him an exit visa. Jewish emigration is a fair test of glasnost, the Kremlin's fidelity to its human rights pledges and its general reliability as an international negotiating partner. There should be close attention to what Mr. Shevardnadze says on this issue -- and to what the Kremlin does.

There is also the question of arms control. The Soviet foreign minister's meeting with Mr. Shultz should bring within early reach a summit at which President Reagan and Party Secretary Gorbachev sign an agreement long in the works to eliminate all of the two countries' intermediate-range nuclear missiles. The meeting could also bring, at least within sight, a much larger agreement to reduce strategic offensive arms by half. Judging by Kremlin hints, this result does not necessarily hinge on a concession by Mr. Reagan on the Strategic Defense Initiative.

All this puts a real burden on Mr. Reagan, puts him to the test. The short time in office remaining to him, the inexplicable events at Reykjavik and his recent political embarrassments combine to generate a good deal of suspicion -- and not only on his right -- that the president could yet do something truly imprudent. On its part, Congress has to be careful the strictures it has adopted to push a seemingly reluctant president to the negotiating table do not become, now that he is there, unwise checks on the American hand.

On Jewish emigration and the full human rights agenda, meanwhile, the president and Congress together need to make sure that the pressure is kept on in an unambiguous and constructive way