Sweden's subtle shift to the right, in which a majority of its voters favor braking but not reversing the grwoth of its extensive and costly welfare state, has thrown the country into political confusion.

Four major parties have made a variety of appeals across the political spectrum during the final weeks of campaigning for the Sept. 16 national election.

On the right wing, the Conservatives, who have been gaining support steadily with their campaign promises to cut taxes and limit government power, are exhorting Swedes to "vote no to socialism" with campaign posters featuring an almost cloudless blue sky.

The Center Party has been speaking in ecological slogans and promising Swedes to protect the environment for their children. Some children are prominently pictured on the Center Party's green campaign posters.

The centrist Liberal Party's campaign is built around its leader, Ola Ullsten, who as Sweden's prime minister for the last year has won wide praise for restoring some stability amid the feuding within the nonsocialist coalition that won the last election three years ago only to face Sweden's worst recession in decades.

On the left, the Social Democrats, who ruled Sweden for 44 years before being ousted in the 1976 election by voters weary of big government and the high taxes it levied, are accusing the nonsocialists of creating financial chaos and warning that it is time to return government to experienced hands.

Of the proliferating number of minor parties -- whose increasing if still marginal support in public opinion polls reflect a growing dissatisfaction here with the major parties -- only the Communists are expected to win the 4 percent of the total vote required to qualify again for representation in parliament.

Only the tacit support of the Communists in parliament had kept the Social Democrats in power in the late 1960s and early 1970s, as their vote steadily eroded in successive elections. Sweden, like its welfare-state Scandinavian neighbors Denmark and Norway before it, was moving gradually away from one-party, left-of-center rule after reaching the limits of growth of modified state socialism.

In 1976, the Center, Liberal and Conservative parties finally won just over 50 percent of the vote and control of parliament with their joint antisocialist theme -- "It's time for a change" -- and late campaign scares about nuclear safety and a threatened takeover of private businesses by left-wing labor unions.

The nonsocialist parties (or "bourgeois" parties, as many Swedes call them) governed first for two years as a three-party coalition and then for nearly a year through the minority Liberal Party government of Ullsten.

They brought Sweden out of its recession and into a rapidly accelerating economic boom by involving the government more deeply in the economy than the Social Democrats ever dared.

The bourgeois governments took over the failing shipbuilding industry, combined the largest steel companies into one corporation with the government as a partner, and took an important role in the direction of the big wood pulp and paper firm. Their subsidies for these ailing industries and the creation of replacements for lost jobs created an unprecedented budget deficit.

"We succeeded in showing Sweden that we would take social responsibility for the protection of jobs during an economic crisis," said Olof Johanson, a fast-rising Center Party member of parliament.

The nonsocialists defend their governments' heavy investment in private business as an emergency measure "to buy time" until Swedish industry can reshape itself in better years to meet increasing competition abroad. Carl Tham, a close Ullsten adviser who is the Liberal government's minister for coordination and energy said: "We do this grumpily. The Social Democrats would have been enthusiastic about it."

"After 44 years of one-party Social Democratic control," Tham said, "the Swedish people have finally experienced what is normal in most Western countries. We have had two nonsocialist governments since the 1976 election and the country did not fall apart. Now we are having a general election that also is more like those in other countries."

The results of the latest opinion polls, made public here this weekend, reveal a growing independence among Swedish voters. While support for the Social Democrats remained at a relatively low level for them of 43 percent, support for the minor parties, including the Communists, rose to a potentially disruptive 10 percent, and allegiances fluctuated widely among the three big nonsocialist parties.

Center Party leader Thorbjorn Falldin demanded late in the 1976 campaign that Sweden stop its fast-growing nuclear energy program because of the dangers of reactor accidents and the problems involved in disposing of nuclear wastes. With Swedes divided into two almost equal camps on this emotional issue, Falldin's call accelerated defections from the Social Democrats to the nonsocialists, particularly the Center Party.

But news of the Three Mile Island nuclear accident in the United States earlier this year threatened to turn this month's election into a nuclear referendum that would immeasurably help the Center Party. The Social Democrats then switched from all-out support of the very nuclear energy program they promoted over the years to a proposal for a separate referendum on the question, which now is scheduled to be held in March taking away the Center Party's issue.

The Liberal and Center parties also have quarreled with each other during the campaign and refused to cooperate with the Conservatives. Voters seeking to support a nonsocialist coalition against the Social Democrats have found that the coalition no longer seems to exist.

The big gains on the right in the opinion polls have been scored by the Conservatives (or Moderate Coalition Party, as they have called themselves for a decade). They hit a campaign high of 19 percent support in this weekend's poll, compared to the 15 percent of the vote they won in 1976.

According to Swedish pollster Hans Zettererg, the credit for this rise and for the growing public demand for tax cuts here should go to the Conservative leader, Gosta Bohman.

"Like John Kennedy in the early 1960s in the United States," Zettererg said, "Bohman has convinced the Swedish people that taxes can be cut."

By election day, however, the disarray among the nonsocialists and the rise in minor parties could put the Social Democrates -- with silent support of the Communists -- back into power by default. Although their popularity has not budged above the hard-core 43 percent in campaign polls, the machinery of the party organization and its labor union foundation can be counted on to turn out that vote.

Opposing politicians credit Social Democratic leader Olof Palme with wisely changing his campaign tactics. In 1976 according to postelection analyses, Aome hurt this party with what voters saw as an intellectual arrogance, especially in television interviews and debates.

"We're seeing a different Palme this year," said one political observer. "He has stayed out of the spotlight to travel the entire country, shaking hands in old folks' homes and hospitals, humbling himself."

Former prime minister Palme is running for his political life. If the Social Democrats lose again after three previous elections in which the size of their vote shrank, he is liable to be replaced as party leader at the 1981 party convention.

As their fortunes have declined, the Social Democrats have suffered an internal split between those who want to refine rather than extend the welfare state and those who favor taking another giant step: labor union control of Swedish businesses.

Union leaders want the next Social Democratic government to pass legislation requiring Swedish firms to pay a sizable portion of their profits each year into union-controlled investment funds that would then buy stock in the firms until they gained controlling interest.

The plan cost the Social Democrats many votes in the 1976 election. Sweden is one of the most thoroughly unionized countries in the Western world, but voting patterns and public opinion polls show that many union members oppose this step towards "guild socialism" in Sweden, where private enterprise has coexisted with the welfare state for more than four decades.

The Social Democrats temporarily shelved the controversial plan before this election campaign, but it stands a good chance to become party policy at the 1981 party convention.