For Thorbjorn Falldin, the moralistic sheep farmer whose election victory ended 44 years of Social Democratic rule here, the merry month of May has been a nightmare from an Ingmar Bergman film.

"I have asked myself whether it was worth this price to be in the public spotlight," Prime Minister Falldin told a startled nation earlier this month. "I am working on the question of how much my family and I should be prepared to sacrifice for the exposed position of a prime minister."

Falldin, 52, who quotes the Bible as readily as the price of grain, had just lost a libel suit against a crude newspaper satire. The article in Aftonbiadet - for which its editors apologized - had predicted that Falldin would end his days in a lunatic assylum, the degenerate product of rural inbreeding.

A few days later, Falldin's personal agony reached a new depth. He was compelled to tell Parliament, that, yes, a former chief of the national police had drawn up a list of prominent persons who had allegedly patronized an expensive ring of call girls.

"I could directly see that it was a lie," the slow-speaking Falldin said gravely. "I could at once state that it was a lie because I found my own name among the listed customers."

Few in Sweden doubted him. Falldin was swamped with sympathetic offerings of flowers. Indignant letters over the vilification of the premier and the pain suffered by his wife and three children poured into the newspapers.

Last week the minicrisis ended.

"My family and I have come to the conclusion that it is possible to live with the tensions of a prime minister's work," Falldin said.

"I will continue with the job and fight for the things I believe in."

If this act in a Scandinavian drama is over, however, it is now clear that Swedish politics will never be the same. The Swedes, who are far more puritanical than popular imagery of a permissive society suggests, have prided themselves on participating in a politics of issues, of rationality. Swedes like to think they are concerned exclusively with great moral abstractions: the politics of justice, equality and decency. Parties are supposed to stand for clear positions, and personalities are the products of cruder politics, like those in the United States.

Yet with his Checker-type speeches and his appeal for sympathy, the upright farmer from Ramvik has changed all this. This politics of personality has now been firmly planted in the pleasant Swedish political landscape.

"That's tedious," snaps of Olof Palme, the brilliant Social Democrat whom Falldin ousted a year and a half ago. A cool and skilled debater, Palme insists that Falldin's performance is an episode and politics here will still focus on traditional class and economic lines. That, after all, is where Palme excels.

Many of the strongest figures in his own party, however, to say nothing of the coalition that Falldin leads, disagree. They think Falldin has instinctively stumbled into a style with great popular appeal.

Gunmar Myrdal, Sweden's Nobel Prize winning economist and lifetime Social Democrat, says of Falldin. "I understand him. Like me, he is a man from the country who has done something with his life."

Myrdal deplores the fact that Sweden's Freedom of Information Act does "nothing to protect" a politician from the most outrageous abuse by reckless journalists.

Even Tage Erlander, Pales' predecessor as a Social Democratic premier, sympathized over the radio.

"I know how it can hit you," he said. "I was accused of being an alcoholic."

Khell Olof Feldt, the party's bright economic spokesman, readily acknowledged that Swedish politics has become more personal. The Social Democrats are big on local party meetings but now they don't want to hear just anybody. They only want the glamorous figures they have seen on television - Palme, Feldt and Pirgotta Dahl, the party's attractive, 35-year-old energy expert. Feldt says:

"Falldin's biggest asset in his personality, his honesty, his conviction. He has shown he is a human being with weaknesses and not an unreal man of steel. He has consolidated his position."

Unsurprisingly, Falldin's political partners in the "bourgeois" coalition now ruling here mostly agree, although some are bitter about it.

"Falldin has exploited his family, his background, his image of an honest man taking care of the country," says one key ally who asked that his name not be used. "He's a big hypocrite."

Genuine or false, there is an inexorable logic in Falldin's discovery of personalized politics. Like other more or less successful northern democracies, there is little to choose here between the major political formations, apart from rhetoric. In office, they behave much the same way, running private property welfares states with a large measure of state intervention.

The Falldin coalition, supposedly in favor of more free enterprise, "has increased state control of the economy more than any ruler since Gustavus Adolphus in the 17th century," a shrewd and dispassionate official quips.

"They have stolen our clothes," complains Myrdal, the Social Democrat.

The most sophisticated businessmen who backed Falldin's coalition are not unhappy about the change in the state of affairs.

"There is no room in Swedish politics for big issues," says Curt Olsson, the clever president of Enskilda Bank, Sweden's biggest. "We would welcome this. It means less abrupt change."

Falldin, however, how faces a tough problem. As one of his allies put it, "He is trapped as an honest man."

Falldin campaigned vigorously here on a promise to close down Sweden's five nuclear plants unless they could be proven safe. But his first act in office was to start up a sixth. His coalition partners and most of Sweden are convinced that the good life depends on more nuclear energy, not less.

Now plants seven and eight are ready to go. How Falldin will keep his reputation for honesty, keep his political partners in line and satisfy the public demand for home-produced power will tax all his ingenuity.

Sweden will accept that Falldin's name on a list of call girl clients is an absurdity, the act of a Swedish J. Edgar Hoover pursuing a bureaucratic vendetta with little basis in fact. But whether Sweden will buy a nuclear compromise from Thorbjorn the Honest could pose an even tougher test for the Ramvik sheep farmer.