The kaleidoscopic stage seemed like a reincarnation of the 1960s as a parade of jugglers, gypsy violinists and rock bands shared the spotlight with antiwar activists preaching the gospel of pacifism.

A few miles away, another auditorium was being prepared for jurists and witnesses to attend a "nuclear war crimes tribunal" putting the superpowers on trial here this weekend for accumulating atomic arsenals to use against humanity.

For West Germany's Greens movement, the tools of political theater form an essential part of their campaign to attract enough votes in elections March 6 to hold the balance of power in the next government.

The peace concerts and people's courts, however, scarcely convey the monumental impact that the countercultural group could bring to bear on more than three decades of postwar democratic stability in this country. The Greens' strong opposition to deployment of new American missiles here has made their showing in the elections a potent symbol for the Atlantic Alliance.

The electoral chances of the Greens and their potential role in parliament have become obsessive themes for voters and politicians alike.

The Social Democrats, who have sought to cut into the Greens' support by stressing antinulcear and ecological issues, now seem resigned to falling short of a majority victory over the Christian Democrats.

If that happens, party strategists say the next best outcome would be for neither the Free Democrats nor the Greens to win the 5 percent of votes required to hold seats in the Bundestag. That result would ensconce the Christian Democrats in power and leave the Social Democrats the sole voice in opposition.

While the centrist Free Democrats' hopes remain marginal, the Greens continue to show that their small party contains a solid constituency in mostly young voters.

The polls vary, but the latest surveys indicate that the Greens will win between 5 and 6 percent. If this forecast is correct, the Greens will pose an excruciating dilemma for the Social Democrats after March 6.

If the Social Democrats maintain their current 43 percent standing, they will have to decide whether the prospects of governing with what many regard as a suspicious and whimsical partner are better than a sustained term in opposition.

The right wing of the Social Democratic Party, led by former chancellor Helmut Schmidt, abhors the notion of working with the Greens during a critical period for West Germany's economy and security.

But leftist elements contend that the party cannot shirk its responsibilities after promising in the campaign to revive the economy with a jobs program and to defuse East-West tensions by seeking a compromise that would prevent deployment of Pershing II and cruise missiles scheduled later this year.

The rift within the Social Democrats, well concealed so far beneath the facade of party harmony, has caused their candidate for chancellor, Hans-Jochen Vogel, to dance around the question of a tacit alliance with the Greens.

In an interview with the political weekly Die Zeit, Vogel said that "a coalition lacks all the necessary preconditions. The Greens must decide for themselves if they want me or Helmut Kohl as chancellor, but I have no concessions or special offers to make to them."

On the other hand, Vogel added, "I would see no sense in refusing to allow myself to be elected by a majority of deputies delegated by the people just because there are Greens among them. The country still has to be governed, or are we going to close down the Bundestag in that case?"

Such ambivalence amuses the Greens' red-bearded leader, Lukas Beckman, who notes "how ironic it is that they call us unstable and uncertain when they cannot even decide themselves what they want to say to us."

"We have told the Social Democrats that we will tolerate their government if they accept two conditions," Beckman said in an interview here. "No atomic power plants and no deployment of nuclear missiles . . . but they find it impossible to say openly if they are against the missiles or atomic energy."

Other Greens leaders also voiced exasperation with the Social Democrats' mixed attitudes, despite clear signals that the Greens are ready to drop their more outlandish notions about restructuring the economy, at least for the time being, in order to fulfill their antinuclear objectives.

"We are already working well with Social Democrats at the grass-roots level," said Wolfgang Ludwig, a key spokesmen for the Greens on the missiles. "It's only at the top where they treat us with distrust. I guess they are trying to preserve as many options as possible."

Petra Kelly, a highly popular antinuclear activist, also chuckles over how "the Social Democrats are changing voices and positions every few days."

"But Vogel knows he cannot be chancellor without us," she said. "We are still expecting them to talk with us right after March 6."

While the major parties have stressed pocketbook issues such as rents and taxes in recent weeks, the Greens have successfully fought to keep the missile controversy in the forefront of the campaign.

Recognizing that voter alarm over increased joblessness was not helpful to their vision for a post-industrial society, the Greens have conducted lively rallies featuring rock entertainers and well-known figures, such as novelist Heinrich Boll, who espouse their causes.

As the climax of their antimissile election effort, the Greens have brought international peace activists here this weekend, notably the Nobel Prize-winning biochemist George Wald, Daniel Ellsberg and Phillip and Daniel Berrigan, to attend what is called "the Nuremburg tribunal against first-strike and mass-destruction weapons in East and West."

The conference will also allow for discussions of ways to prevent deployment of nuclear missiles through civil disobedience.

Although they express "absolute confidence" of winning enough votes to halt the missiles through parliamentary clout, the Greens contemplate demonstrations, sit-ins and strikes to sabotage deployment if they fail to win Bundestag seats.

"Our efforts to stop a new generation of weapons from coming here take precedence over everything else," said Beckman. "It would be a great tragedy if the missiles are deployed, for if they are as dangerous as they seem, I think it would provoke the Soviets to take direct military action, though I don't know of what kind."