THE REAGAN administration's application of limited sanctions against Poland for crushing Solidarity has worked pretty well. In the latest phase, Gen. Jaruzelski reluctantly released the last two political prisoners at issue, making good on his pledge to give amnesty to those detained when he imposed martial law three years ago. In turn, the Reagan administration is ending its principal sanction: its veto of Warsaw's application to join the International Monetary Fund. Joining the IMF will help the Poles cope with their immense economic difficulties and keep a measure of their national life in a Western environment.

Some Poles -- and surely, some Soviets -- are not pleased by the tense and unlikely partnership now being confirmed tacitly by Ronald Reagan and Wojciech Jaruzelski. They would prefer the sort of impasse that would force the regime to rely even more than it does on its police and on Kremlin power. President Reagan has critics too. It's interesting evidence of the pragmatism of his overall approach to Europe: He has sought to keep his Polish policy within lines acceptable to American allies and relevant to his second-term bid to the Krem- lin. Some Reagan critics think he should have bargained a bit harder before playing the IMF ace. Others think he should have bargained a lot harder in order to make life untenable for the Jaruzelski regime. But down that path lies an East-West confrontation he clearly wishes to avoid.

Now as always with Poland, everything is tentative. Inside the country, the scarcely concealed equivalent of a multi-party political struggle is raging among factions in the government, the church and the banned (yet unbannable) Solidarity. The maneuvers of the regime and the nuances of the administration would amount to little if the Kremlin decided on a full-scale crackdown. In this context, nonetheless, Mr. Reagan has done what could be done to offer relief to the Polish people and a certain political choice to their rulers.