STOCKHOLM — SWEDISH voters confirmed their growing disillusionment with welfare ideals by ousting the ruling Social Democrats.The Sept. 16 vote, the Social Democrats' worst setback since 1928, is being hailed by many as the end of an epoch in which the Social Democratic Party governed Sweden for all but six of the past 59 years. "It's a big setback for us," acknowledged Prime Minister Ingvar Carlsson, who announced his resignation Sept. 16. The winner of the election is Sweden's four-party conservative coalition, led by the Moderate Party. The coalition gained 17 seats in parliament, attaining 170 of the 175 seats required for a majority. The Social Democrats declined to 154 seats. The election's relatively even outcome throws the Riksdag into tumult. Lacking a majority in the Riksdag, the coalition of four conservative parties may be forced to cooperate with the right-wing New Democracy party to gain support for legislation - a move strongly opposed by center-right party leaders. The 10-month old, populist New Democracy party has gained much attention here recently. Though politically unaligned, New Democracy is said to be a "party of discontents," including blue-collar workers, white-collar executives, and street people. It captured 6.9 percent of the vote, and will be a critical "swing" factor in the parliament. The Christian Democratic Party, supporting traditional values such as church, ethics, and family won its first parliament seats. The Greens, in the Riksdag since 1988, lost the 4 percent support required to stay in national office. "It's a chaotic situation - exactly what we warned about," says Mr. Carlsson. Throughout his election campaign, the prime minister had questioned whether the four parties in the coalition could unite, let alone command a majority, without cooperating with the controversial New Democracy party. In 1982, infighting toppled a non-Socialist coalition government in power since 1976. T is "our best election result ever," counters Carl Bildt, leader of the conservative Moderate Party. "We've got a clear mandate for change." Tall and boyish-looking, Mr. Bildt will likely be named Sweden's next premier in two or three weeks. Clearly, Swedish voters want a change. According to one analyst, their vote was for lower taxes, less government, and more private initiative. They are tired of shouldering the world's heaviest tax burden and prepared to prune their luxuriant cradle-to-grave welfare system, the analyst said. Problems have been appearing for some time in Sweden's much-touted "middle way," between capitalism and socialism. Since the 1986 assassination of Prime Minister Olof Palme, economic and social change have worked to reshape the Swedish model into a European-style market economy. "We're starting to get more and more like the rest of Europe," comments Olof Ruin, head of the political science department at Stockholm University. Mr. Ruin anticipates a redefinition, rather than abolition, of the Swedish model. He expects a continued emphasis on equality, solidarity, welfare, an active labor market, and universal benefits, rather than tax cuts, privatization, and diminished social services. But the days when the government worked hand-in-hand with labor to keep the economy running smoothly may be over. The country is deep in recession. Unemployment has risen to over 3.1 percent and is expected to climb to 4 percent or more by next year - a shockingly high level for Swedes, who have grown up with almost no unemployment. Growth in Sweden's gross domestic product plummeted to 0.3 percent from 2.1 percent a year earlier. Growth is expected to be negative 1.1 percent in 1991. "It's the historic failure of the 'middle way' policy that has led to the current crises," Bildt claims. "Unemployment is rising faster in Sweden than in any other European country right now." Bildt must now build a minority government of non-Socialist parties. The exact composition of such a coalition remains uncertain, but Sweden's conservative shift is unmistakable.