WARSAW, NOV. 26 -- Prime Minister Tadeusz Mazowiecki, forced by a political unknown into a humiliating third place in the initial round of Poland's first popular presidential election, announced the resignation tonight of his 15-month-old Solidarity-led government.

"Society has made a choice, and I have drawn a conclusion from it," Mazowiecki said, adding that he and his ministers would remain in office until the new president -- to be chosen in a runoff vote in two weeks -- could appoint a successor.

"We accomplished a great deal over the past year," Mazowiecki said. "The election results showed, however, that the government's political line had come into question."

Mazowiecki's abrupt resignation and chastening election defeat by Solidarity union leader Lech Walesa and obscure emigre businessman Stanislaw Tyminski were viewed widely here as a result of his government's failure to sell radical free-market reform to Polish voters -- particularly blue-collar workers, farmers and the young. In the aftermath of Sunday's election, it seemed apparent that the first post-Communist government in Eastern Europe was out of touch with the poor and the less-educated.

Voters today used words like "arrogant" and "elitist" to describe a government that last year was hailed as a triumph of democracy over communism. "Grave mistakes were made in our information policy before and during the election," Mazowiecki's spokesman Adam Szostkiewicz said today. "This government failed to explain the many successes it achieved during the last year."

Mazowiecki, whose reforms won accolades from Western governments as the most courageous and consistent in the region, was eliminated from presidential contention by the strong showing of Tyminski, a 42-year-old emigre entrepreneur who claims a personal fortune of $5 million from businesses in Canada and Peru but who was a political nonentity here before the month-long election campaign.

Walesa, as most analysts here had predicted, finished first in Sunday's voting with about 40 percent of the vote, while Tyminski won 23 percent and Mazowiecki 18. None of the other three presidential candidates won more than 10 percent.

Enthralling audiences with visions of prosperity just around the corner, Tyminski rocketed from political obscurity to a spoiler's role that enabled him to topple the government, shake Walesa's political confidence and plunge Poland into its deepest political crisis since the peaceful overthrow of communism last summer.

Mazowiecki said tonight that his view of Polish democracy "and the establishment of a foundation for a healthy economy had been called into question. During this campaign, many promises were made that could not be kept. The government and I personally were charged with serious and very often demagogic accusations."

Mazowiecki also made it clear that he blamed both Tyminski and Walesa -- who had handpicked him as prime minister -- for undermining his government. For his part, Walesa acknowledged today that the Solidarity movement he founded in the early 1980s had, with Sunday's vote, "lost its breath and its steering ability. . . . We have not answered the challenges of the time."

Walesa, who had disparaged Tyminski during the campaign as "a man from the bush" and threatened to withdraw rather than face him in a runoff, made clear today that he would run, even though he found the prospect distasteful.

The seismic shock generated by Tyminski's improbable showing seems likely to be felt across Eastern Europe. From Sofia to Budapest to Prague, Poland has been watched as a gauge of the possibilities and limits of aggressive free-market change. Sunday's crash landing for Mazowiecki may give the jitters to all newly elected leaders in the region and could cause a retreat from economic reforms that demand sacrifice from workers.

Tyminski, a bland-featured man in horn-rim eye glasses who stands at the epicenter of Poland's political shakeup, built his businessman-knows-best campaign on two simple arguments:

First, he told voters that he had struck it rich in Western business ventures and, therefore, was an authority on how capitalism works. Second, he claimed, albeit with no hard evidence, that the old Solidarity crowd of Mazowiecki and Walesa was conspiring with former Communists to sell off Poland's industries at fire-sale prices.

Asked today why Polish voters found him so attractive, Tyminski said:

"For the first time after the war, {I offer Poles} the chance to earn money, money that would exceed their cost of living. . . . I would like to take my jacket off, roll my sleeves up and go to work to make this country rich."

Tyminski has been notably vague on how he would make Poland rich or how he could improve on the free-market reforms that have made Poland attractive to international lending agencies and won it $10 billion in Western credits. Voters in the streets of Warsaw said they voted for Tyminski not because he made sense or because he had a workable program, but out of anger at what they described as the smug, we-know-better attitude of Mazowiecki and his Solidarity ministers.

"This vote is a measure of frustration. Solidarity has slowly begun to form an elite -- like the Communists we got rid of last year. Our nation is very resentful of elites. This is a proof of the nation's rage," said a retired Warsaw businessman.

Voter exit polls Sunday showed that Tyminski ran strong among blue-collar workers, rural residents and young people -- segments of the electorate that had been considered strong supporters of Walesa. Walesa, indeed, seemed to sense early this year the frustration of working people with a government that he charged was controlled by "eggheads" in Warsaw.

Walesa, who remains the single most potent political figure in Poland, forced the presidential election by accusing Mazowiecki of building capitalism on the backs of the working man and of moving too slowly to rid government and industry of holdover Communist officials. In doing so, however, Walesa splintered the unique alliance of workers and intellectuals that had held together for nearly a decade under the banner of the Solidarity movement.

As Solidarity splintered, Tyminski moved in. In the most industrially blighted parts of southwest Poland -- where pollution causes severe health problems and where unemployment is expected to skyrocket next year as money-losing factories are closed -- Tyminski finished in a near dead-heat with Walesa.

A much discussed commentary in Poland's largest daily newspaper, Gazeta Wyborcza, said today that Tyminski found a disaffected audience in what it called the "second Poland." In this "second Poland," well away from the capital and major cities, the newspaper said, "the uneducated people and inhabitants of smaller localities did not understand the reforms, did not accept the sacrifice, did not support the government any longer." Under the Mazowiecki government, earning power of the average worker has declined about 30 percent, while unemployment -- offically unknown during the Communist era -- has exceeded 1 million.

In the week before Sunday's election, Tyminski made a poorly documented claim that Mazowiecki had committed "treason" by selling off state-owned industry at below-market prices. The accusation, which appeared to be based on a misreading of government documents, triggered howls of protest from the government, which filed criminal charges of slander. The Polish press lambasted Tyminski as mentally unbalanced and a danger to Polish democracy.

These attacks, ironically, may have helped Tyminski. "Hostility {toward the government} has turned out to be so big that, just as under Communist rule, press reports disavowing Tyminski produced exactly the opposite effect," concluded Gazeta Wyborcza, which had supported Mazowiecki and described Tyminski as "insane."