THE POLISH crisis does not end, it merely goes from one stage to the next. That is what happened this week when the Kremlin seemed to put on the shelf, for the time being, any immediate plans it may have had to crush Poland's experiment in socialist reform. The evident Soviet strategy now is to continue a war of nerves by political means -- to encourage hard-liners in the Polish leadership to undo some of the concessions won previously by the workers and by those in the party who are attempting, for reasons of belief or tactics, to conciliate them. At the least, the Kremlin wishes to assure that no further concessions are granted.

It is assumed in most discussions of Soviet policy that there is a line in Poland whose crossing will bring the Soviets in. Usually that line is said to be the formal dominance of the local Communist Party and firm Polish adherence to the Soviet-led Warsaw Pact. It is precisely the genius of the national revival begun by Solidarity last summer to stay within those twin traces, or to make it very difficult for Moscow to claim that the Polse are straying beyond them.

Solidarity has accomplished this in two ways. With the Catholic Church, it has taken the flag of Polish nationalism almost entirely away from the Soviet-sponsored political leadership. It has made what is, in terms of Polish history, a startlingly well-disciplined and so far successful effort to keep public opinion from spilling over into openly anti-Soviet forms.

With great imagination, moreover, Solidarity has gone beyond trying to consolidate itself as a workers' movement. It is also seeking to infiltrate and democratize the official party and government structures. For instance, Lech Walesa now suggests that the workers, instead of ignoring the rubber-stamp parliament, summon its deputies to factory meetings and insist that they take up their grievances. The same process of reform-from-below is growing on in respect to elections to the coming party congress.

It will not be easy going, in brief, for a Soviet strategy aimed at aggravating Polish differences and wearing down Polish nerves. There is a tenative "coalition of moderates" in the workers' movement, party and church, and it is growing firmer. If this continues, the Kremlin may find itself with an even starker choice of standing back and letting the Poles take their own road to socialism, and intervening to ensure that they stay on the Soviet road.