|Polish Prime Minister Donald Tusk, centre, will likely turn to his current coalition partners if he wins [EPA]
Poles are voting in parliamentary elections that will determine whether the country continues on its conciliatory course with Russia and Germany, or whether it returns to a more combative stance with its historic foes.
Polls showed incumbent prime minister Donald Tusk's centrist and pro-EU party in the lead ahead of Sunday's vote , but outspoken former prime minister Jaroslaw Kaczynski's conservative-nationalist Law and Justice party narrowed the gap in some polls at the end of campaigning.
No party is expected to be able to rule alone and Tusk is likely to turn to his current coalition partners, the Peasants' Party, if he wins.
But opinion polls suggested the left-wing Palikot's Movement, a new party which supports gay rights, abortion and legalisation of soft drugs, could emerge as a potential partner.
Tusk, who steered the country of more than 38 million people safely through the 2008-09 global financial crisis, has portrayed himself as a guardian of stability and said he will continue his cautious approach to economic reforms if he wins.
"At stake in this election are security and the stable development of our country. In my view, only PO [Civic Platform] guarantees that," Tusk said on Friday.
To his supporters, Tusk is a moderate leader who has promoted stability and good relations with Germany, Russia and the EU. They point to the fact that the economy has grown steadily on his watch.
His opponents accuse him of lacking the courage to make ambitious reforms in a country with significant problems, like high unemployment at around 11 per cent and heavy state regulation that stifles businesses.
Law and Justice leaders have promised more state involvement in the economy, including a bank tax and higher taxes for the rich, and vowed to wind down large-scale privatisation carried out since Civic Platform took power in late 2007.
"If Poland becomes a strong, developed country, we won't have to privatise Polish companies, sell state firms for peanuts or privatise hospitals," Kaczynski told the Fakt tabloid.
Poland's main immediate challenge is to curb the public debt and deficit, which ballooned during the financial crisis.
Ratings agencies have said they could downgrade Poland if it does not swiftly act to reduce the budget deficit, expected to reach 5.6 per cent of gross domestic product this year, and the public debt, expected to reach 53.8 per cent of GDP this year.
Economists doubt Law and Justice would be able to meet the challenge and a short-term sell-off would be likely on Polish financial markets if it won.
The current coalition, however, has failed to deliver on the far-reaching liberal market reforms Tusk originally promised.
The rise in support for Palikot's Movement came as a surprise. It was founded by a maverick lawmaker, Janusz Palikot, who is fighting the power of the Roman Catholic church and favors many liberal causes.
Palikot's party was in third place in some recent polls, ahead of some established parties, and appears to be benefiting from disillusionment with them and increasing secularism in this conservative, mainly Catholic country.
If Tusk's Civic Platform wins on Sunday, it would make history by becoming the first to ever win two consecutive terms since the fall of communism in 1989.
However, polls show it unlikely to win enough votes to have an outright majority in parliament, meaning it would likely need to find a coalition partner. And any prolonged uncertainty over the shape of the coalition
could unsettle financial markets in Poland.
More than 30 million people are eligible to vote. They will elect 460 legislators in the lower house, the Sejm, and 100 to the upper chamber, the Senate.