WARSAW, DEC. 9 -- Solidarity leader Lech Walesa, the living symbol of Eastern Europe's revolt against communism, swept to the Polish presidency today with a landslide victory over challenger Stanislaw Tyminski, according to exit poll projections.

Walesa's election as Poland's first popularly chosen president ended a bitter campaign that split the Solidarity alliance and provided an opening for Tyminski, an emigre businessman whom Walesa accused of being a front man for a counterrevolution by Poland's former Communist rulers.

Walesa received 75 percent of the vote in today's presidential runoff, according to projections by the German polling firm Infas. Tyminski's 25 percent share represented a scant 2 percentage-point increase over his showing in the first round of the presidential vote.

Leaning out of a window of his headquarters in Gdansk tonight, a relieved and jubilant Walesa promised a crowd of supporters: "I will be your servant, I will work for all of you. We have to work together, and I will not play around -- I will work hard every day."

Walesa told state television that "really important and difficult tasks are ahead of us," and said his share of the vote was an important popular mandate. Supporters greeted him with a glass of champagne and a chorus of the Polish song "Sto Lat" -- "May he live 100 years."

The victory was a personal triumph for the burly, 47-year-old former electrician and hero of Solidarity's 10-year struggle against communism. Walesa will succeed Communist Gen. Wojciech Jaruzelski, whose imposition of martial law in 1981 sent Walesa and thousands of other Solidarity activists to jail.

Walesa was heavily favored to win in preelection surveys, but pollsters had not ruled out an upset by Tyminski, whose campaign exploited fears about worsening unemployment and falling living standards.

Tyminski, a Pole who returned to his native country to run for president after 21 years in Peru and Canada, claimed that Solidarity's economic policies would turn Poland into a land of "white slaves" and called instead for a "democracy of money," which he did not explain.

But alarm about Tyminski, whose campaign staff included many former secret police officers, apparently overrode popular concerns about the economy and Walesa's autocratic style.

Scores of Poles interviewed after voting said they had chosen Walesa to ensure stability and order and to keep the presidency from the hands of a man Walesa had called a "con man" and front for ex-Communists trying to turn back Solidarity's democratic revolution.

Exit-poll projections by Infas showed Walesa's support was high in all segments of Polish society, including industrial workers, farmers and pensioners who had supported Tyminski in the first round, held two weeks ago.

Polling data showed that Walesa also picked up nearly all of the votes cast in the first round for Solidarity Prime Minister Tadeusz Mazowiecki, who finished behind Tyminski in third place. Surprisingly, Walesa also was supported by more than half of those who voted for the Communist Party's candidate in the first round.

Tyminski's greatest support came from small cities, towns and villages, where voters had less exposure to the campaign and where uncertainty and resentment of old Communist elites and new government policies run high.

Tyminski tonight vowed to continue his "political fight, even if I have to do it in prison," and said he would consider forming his own political party.

Walesa, angered by Tyminski's claims during a televised campaign news conference that he had information that would incriminate the Solidarity leader, vowed earlier this week to put Tyminski in handcuffs. Tonight he predicted that Tyminski would "fade away as quickly as he appeared."

Today's result was an apparent vote of confidence in Poland's free-market economic reforms, now the most far-reaching and rigorous in Eastern Europe, and for stability when governments across the region face growing dissatisfaction over hardships imposed by post-Communist reform.

But even in defeat, Tyminski altered the assumptions of Polish politicians by showing that popular tolerance for painful austerity programs is hardly unanimous.

During the campaign, Walesa pledged to accelerate the pace of the reforms and "take an axe" to what remains of the country's old Communist bureaucracy. But Walesa pronounced himself "terrified" at the public discontent revealed by Tyminski's strong first-round showing and recently softened his rhetoric to say that the reform program would be "adjusted to what society can accept."

Walesa could be sworn in as president as early as Dec. 21, according to parliamentary officials. Tonight, he said he would announce composition of his new government in several days. The team is rumored to include former Solidarity parliamentary leader Bronislaw Geremek, a Mazowiecki stalwart, as foreign minister.

As president, Walesa will face an extraordinary leadership challenge. He must preside over massive restructuring and privatization of Polish heavy industry, a process that is expected to eliminate 2 million jobs by the end of next year. To accomplish this, he must prevent the country from becoming paralyzed by strikes.

During his campaign, Walesa promised industrial workers that unemployment would be only a transitional problem and told several steel mill rallies that he would not close plants until new jobs had been found for their workers. Walesa's critics in the Mazowiecki government said he was making promises he could not keep.

In his televised victory statement, Walesa promised Poles that their dreams could be achieved through discipline and hard work. "Through solidarity and through common action we have won our freedom. And only we can decide what we shall do with this freedom in the future," Walesa said.

He asserted that "not a single group or a single man will be able to say, 'There are no prospects in front of me.' In Poland there is work for everyone. We have to change a lot and modernize a lot. . . . But first of all we have to help ourselves."

Walesa's triumph culminates a career that began in 1980, when, as an unemployed electrician blacklisted because of illegal union activities, he leaped the fence of the Gdansk shipyard to join a strike that ultimately secured the right for independent unions to organize.

In the decade that followed, Walesa showed extraordinary courage and political cunning, plotting along with key Solidarity advisers the strategy of negotiation and labor pressure that, along with a deteriorating economic situation, ultimately pushed the Communist Party from power.