WARSAW -- Lech Kaczynski, a conservative, won Poland's presidential runoff yesterday, on a platform combining traditionalist Roman Catholic values with promises to limit corruption and to shore up benefits for the poor.
Partial results found that Kaczynski, Warsaw's mayor, had won more than 54 percent of the vote. This was an 8-point advantage over Donald Tusk, a former ally who has favored a business-friendly approach.
Kaczynski's victory sealed a move to the right in the European Union's biggest former East-bloc newcomer, after his Law and Justice party, and Tusk's moderate Civic Platform, crushed the governing leftist party, the Democratic Left Alliance, in general elections last month.
A moderate nationalist who is wary of deeper European integration, Kaczynski replaces Aleksander Kwasniewski, who by law could not run after two five-year terms in the presidency.
Kaczynski said that Poland, which joined the EU after a vote in 2003, may hold a referendum on adopting the euro in 2010.
''The question of the euro should be resolved through a referendum, which could take place in 2010," Kaczynski said.
Kaczynski has expressed reservations about joining the common European currency, the euro, but said the referendum was necessary because adopting that currency meant giving up part of Poland's sovereignty.
The election between Tusk and Kaczynski, former activists in the Solidarity union movement that toppled communism in 1989, became a plebiscite on whether the country of 38 million needs a more free-market approach, or more aid to its citizens.
Kaczynski, who portrayed Tusk as a heartless free-market zealot, extended an olive branch to his rival. He urged him to join forces in the government.
''I want to call . . . for us to quickly conclude work on the government.
''I will approach Donald Tusk, who fought superbly in this campaign," Kaczynski told supporters.
In the campaigns, the Kaczynski twins, Lech and Jaroslaw, also a leader of the Law and Justice Party, combined Christian values with skepticism of free markets.
The message appealed to many poorer Poles.
The brothers promised to build what they called a ''Fourth Republic," in a break with the corruption that characterized the post-Communist ''Third Republic."
Sleaze and political patronage was reported in abundance during the four-year rule of the left. The leadership's popularity sank, despite its success in bringing Poland into the EU.
Transparency International has rated Poland the most corrupt country in Europe, putting it in 70th place in its 2005 ranking in perceptions of corruption worldwide.
The victories in both elections are a sweet reward for the Kaczynski twins, 56, after years of never making it to the top in politics.
The former child stars of a 1962 movie called ''The Two Who Stole The Moon," the brothers were kingmakers in previous center-right governments, but were shunned for top posts.