Petr David Josek, Associated Press
Donald Tusk of the opposition Civic Platform party celebrates landslide victory with his supporters Sunday in Warsaw.

WARSAW, Poland — A pro-business opposition party that wants Poland's troops out of Iraq ousted Prime Minister Jaroslaw Kaczynski's government in parliamentary elections Sunday, as Poles opted for leadership offering a more cooperative approach to the European Union.

Donald Tusk's Civic Platform party led with 41.1 percent of the vote after 11 percent of the ballots were counted early today, and exit polls for TVN24 private television showed the party winning 226 seats in the 460-seat Sejm lower house.

That was short of the 231 needed for a majority — but close enough for it to join with a smaller party to form a government.

"Today I am the happiest person in the world," a teary-eyed Tusk told supporters. "People in Poland voted today to choose their own fate and have put a great responsibility a great task on our shoulders. We undertake this great responsibility."

Kaczynski conceded defeat late Sunday, saying, "We didn't manage in the face of this unprecedented broad front of attacks," referring to the opposition's campaign.

His Law and Justice party got 31.6 percent of the vote and a projected 156 seats, according to partial results and exit polls. Complete results are expected either later today or Tuesday.

A hard-fought campaign generated voter turnout of 55.3 percent, higher than any parliamentary elections since the fall of communism in 1989, according to an exit survey conducted by the PBS DGA polling institute.

The election result means Poland will no longer have twin brothers holding the two highest offices; Jaroslaw Kaczynski's brother, Lech Kaczynski, will remain the country's president with a term lasting until 2010. The 58-year-olds are former child movie stars who as adults became activists with the Solidarity trade union movement that helped topple communism in 1989.

Both Tusk and Kaczynski favor good relations with the United States, but Tusk argues Poland has not gotten enough from its close ties with Washington and wants the country's 900-strong detachment in Iraq to come home. He also says Poland should drive a tough bargain in return for hosting a missile defense base.

It is a stinging defeat for Kaczynski, whose socially conservative party was elected two years ago and has since been criticized for its assertive approach to the EU and efforts to purge former communists from positions of influence.

The 50-year-old Tusk, the favorite to become the next prime minister, said the election showed that Poles want to focus on the economic opportunities presented by the country's membership in the EU, which Poland joined in 2004.