PRAGUE — THE dam has burst, and the wave of rapid change is turning Czechoslovakia into a very different country from what it was only a couple of weeks ago. Until now, the opposition movement headed by Civic Forum has been riding high on that wave, and the formation Sunday of a new coalition government meant that yet another demand by the opposition was met. Still, final victory is far off, and on the eve of the formation of the new government, different opinions within the opposition have been openly acknowledged for the first time.
At the same time, the Communist Party has launched a frantic counteroffensive to avoid disappearing in the multiparty democracy which now seems a distinct possibility.
Civic Forum has not proposed any names for the new government but has suggested that the defense minister should be a civilian and the interior minister a noncommunist.
According to a well-placed source in the opposition, the Forum is still relatively supportive of Ladislav Adamec, the present prime minister who is also heading the new government. But the Forum sees him as weak and rather isolated, and his relationship with the Communist Party is unclear.
In the meantime, Civic Forum has had its first direct talks with the party, at the party's invitation. The talks were relaxed, and the Communist Party representative, new Politburo member Vasil Mohorita, seems sincere, according to opposition sources. The two sides decided to set up a 24-hour hot line.
Hours before the Sunday deadline for the new government, one of the groups in Civic Forum, the Democratic Initiative, criticized the Forum for supporting Mr. Adamec in his efforts to form a new government.
``We think that the Adamec government should not be reconstructed but resign,'' said the Democrative Initiative's spokesman Bohumil Dolezal, and suggested that Valtr Komarek, a leading economist and Communist Party member, should head the new government.
Democratic Initiative is an independent liberal democratic party and one of almost a dozen groups that founded Civic Forum two weeks ago. The spokesman stressed that his group was still part of Civic Forum, but its decision to make public its stand is the first sign that the opposition is not unified on future tactics.
The announcement also came in a lull in the opposition activities. Over the weekend Civic Forum decided not to have any press conferences unless the new government was formed.
The decision to take a break from daily meetings with the press is partly due to the fact that many in Civic Forum are simply exhausted and need a little rest. But some observers here say that the Forum has lost some of its momentum.
Valtr Komarek, who is head of the Czechoslovak Economic Forecasting Institute, has had no comments about the reports that he might be a future prime minister, but at a recent news conference he warned that the battle was not yet won, and he criticized Civic Forum for making too many compromises. Instead, he wanted the Forum to step forward and take charge and stop acting as if it were in opposition.
``An irreversible breakthrough has occurred, but the power structure remains, and compromises mean loss of time,'' he said. ``It is time for the opposition to realize that it is no longer the opposition.''
Meanwhile, the Communist Party is rethinking most of its basic concepts of the last 20 years, including the leading role of the party and the Soviet-led invasion of Czechoslovakia in 1968 which put an end to the reform movement called ``Prague Spring.'' And over the weekend the disarming of the party's police, the People's Militia, started.
The decision to invade in 1968 was ``wrong and unjustified,'' said Vasil Mohorita after a Politburo meeting which started at 6 a.m., a sign as good as any of how urgent the communists think the situation is for the party.
Mr. Mohorita talked about a new political situation with great frankness. Clearly, the party's aim is now to prepare for survival in the multiparty democracy which could be a reality before long.
``The Czechoslovak Communist Party existed successfully for 20 years during the prewar democracy,'' says Jiri Malinsky, a member of a new group in the Communist Party called the Democratic Communist Forum.
The Democratic Communist Forum is one of several new groups within the party, reflecting a new tolerance. The group is pushing hard for the extraordinary party congress to take place on Dec. 20.
The ruling Politburo also seems to think time is important as it has already presented a new action program and the coming weeks are full of conferences on all levels of the party's organization.
And so the fight for power in a different and more democratic Czechoslovakia goes on. Most observers believe that a backlash is impossible, but no one thought a backlash possible in 1968.
Today however, Czechoslovakia, as the next to last of the old communist regimes in Eastern Europe to change, may be able to learn from the others. Also, in Moscow, Leonid Brezhnev is no longer the leader.