Two months after the death of Poland's president in a plane crash, voters face a choice between two visions of the country's future: a smaller state role and more rapid integration with the European Union, or more active government involvement in the economy and a more nationalist foreign policy.

Poland Votes.

Jaroslaw Kaczynski lifted his late brother's granddaughter Eva to cast his vote.

Opinion polls for Sunday's presidential elections show Bronislaw Komorowski of the market-friendly, Civic Platform party with a substantial—though narrowing—lead over the late president's identical-twin brother, Jaroslaw Kaczynski, of the conservative Law and Justice party, which has been more skeptical of the benefits of adopting the euro.

With 10 candidates running, neither man is considered likely to win more than 50% of the vote, as required by the Polish constitution, setting the stage for a second round of balloting on July 4.

"The gap between the two main parties is very, very deep," said Marek Matraszek, founding partner of political consultancy CEC Government Relations in Warsaw. "The welfare state versus free-market division is coming very much into focus."

Most executive power in Poland rests in the hands of the prime minister and cabinet. But the president serves as commander-in-chief of the armed forces and can veto laws, giving him significant influence.

Mr. Komorowski, the speaker of parliament, became acting president after the April plane crash in Russia, in which 96 people died, many of them prominent officials. If he wins, it could make it easier for Prime Minister Donald Tusk, also from Civic Platform, to move ahead with plans to privatize state-owned enterprises, trim pension programs and raise the retirement age in an effort to shrink the government's budget deficit.

Poland prepares for Sunday's presidential vote to replace President Lech Kaczynski who died in a plane crash in April. Video Courtesy of Reuters.

A win by Mr. Kaczynski would likely mean a reprise of the friction that characterized dealings between Mr. Tusk and Mr. Kaczynski's late brother, Lech, who favored robust welfare programs and was often cautious about closer integration with the older, more affluent states of the EU.

Still, with parliamentary elections due next year, Mr. Tusk can be expected to proceed cautiously on social-spending programs to avoid alienating voters, said Mr. Matraszek. "It's not clear that, even with a Komorowski victory, there would be any radical acceleration in reforms," he said.

Analysts say markets would view a Komorowski victory more positively because of expectations of further government cost-cutting. In the wake of the Greek debt crisis, markets have become increasingly focused on government spending. Poland's budget deficit this year is expected to be about 7.3% of gross domestic product, and is projected to drop to about 7% next year. Poland was the only nation in the EU whose economy grew last year.

Another important difference between the two parties is onIn foreign policy,. Mr. Kaczynski's party has placed emphasis on ties with the U.S. and opposition to Russia's efforts to expand its influence in the parts of Eastern Europe once controlled by the Soviet Union. Civic Platform's leaders tend to put priority on ties with the EU and seeking to reduce tensions with Moscow.

Jan Hartman, a professor at Jagiellonian University in Krakow, characterized the electorate as split between the often rural, "conservative, Catholic part of society, the lower classes," who tend to back Mr. Kaczynski's socially conservative party, and "more affluent, more liberal" people in urban areas who favor free-market policies and support Civic Platform.

There has also been debate in Poland about how much longer the country should have troops deployed in Afghanistan, where around 2,000 Polish soldiers are now serving alongside forces from other European nations and the U.S. Mr. Tusk, the prime minister, has said the government will start a discussion with the North Atlantic Treaty Organization on an exit strategy. Law and Justice also says the issue should be discussed, but appears less intent on quickly setting a timeline.