Poles voted this afternoon in a snap parliamentary election that could weaken the grip of the conservative Kaczynski twins and bring in a government ready to speed up economic reforms and improve relations with EU allies.
Opinion polls suggest the Civic Platform, a centre-right opposition party, will attract most support.
However, no party looks set to win outright which would lead to negotiations over a coalition in the European Union's biggest ex-communist country. This election was called two years early after the last coalition collapsed over a corruption inquiry.
The Platform has plans to rebuild relations with EU allies that have suffered under the nationalist brothers. It also aims to pull Polish troops out of the U.S.-led force in Iraq.
Opinion polls have put the Platform between 4 and 17 points ahead of the ruling Law and Justice Party of Prime Minister Jaroslaw Kaczynski and his brother Lech, the president. The polls gave the opposition party up to 47 percent support.
"We have to accept the will of the voters, that's obvious. We won't get angry at the people and lessons from this campaign will be learned," the prime minister said after voting in comments that indicated little optimism.
Platform leader Donald Tusk, tipped to be the next prime minister if his party wins, sounded more upbeat.
"Of course I expect to win, but I also know perfectly well that it will not be easy and the battle goes on until the last minute," he said.
Exit polls are due once voting ends at 8.20pm.
The party of the 58-year-old Kaczynskis has run the country of 38 million people during two years of growing prosperity but constant political turbulence.
The Kaczynskis have fought repeatedly with EU partners and strained relations with Germany and Russia. The opposition also accused the brothers of focusing on fighting corruption instead of reforming central Europe's biggest economy.
"The Civic Platform's economic programme makes more sense to me. The market, not the government, should regulate the economy," said Krzysztof Zawadzki (36) a tax advisor.
Sixty-year-old Maria Choszczyk, a teacher, said: "I voted for Law and Justice. It's the only party that is serious about combating crime and corruption."
Turnout is seen as crucial and stood at 8.4 per cent by 10.30 am, nearly a quarter more than in the last election in 2005. Low participation then - just 40 per cent - is thought to have helped the Kaczynskis.
Financial markets are betting on victory for the Platform. Expectations that it will win, and accelerate Poland's moves to adopt the euro, have lifted the zloty currency to its highest level for over five years.
Some 30 million Poles are eligible to vote. At stake are 460 seats in the lower house of parliament and 100 Senate seats.
If opposition parties won three fifths of the lower house's seats they would be able to nullify the veto by the president, who does not face an election until 2010.