Poles are voting in a parliamentary election that the ruling party of Jaroslaw Kaczynski is favoured to win easily, buoyed by the popularity of its social conservatism and generous social spending policies that have reduced poverty.
Law and Justice is the first party since the fall of communism to break with the austerity of previous governments. Those free-market policies took a moribund communist economy and transformed it into one of Europe's most dynamic.
However, many Poles were left out in that transformation and inequalities grew, creating grievances that Law and Justice has addressed skilfully. Its most popular program, called 500+, gives away 500 zlotys ($A188) to families per month per child, taking the edge off poverty for some and giving more disposable income to all recipients.
However, many of the party's liberal critics fear that another four-year term for Law and Justice will reverse the achievements made three decades ago in this Central European nation, long hailed as a model of democratic transformation.
They cite an erosion of judicial independence, pluralism and minority rights since the party took power in 2015.
Law and Justice's overhaul of the judicial system has given the party unprecedented power over the public prosecution system and the courts.
In reaction, the 28-member European Union has repeatedly warned that the rule of law is threatened and took sanctioning mechanisms that have blunted some of the changes, but not all.
The party has also used tax-funded public media, which under the law should be nonpartisan, to pump out simplistic propaganda hailing the party's achievements and denigrating political rivals.
Polling stations are due to close at 9pm. Exit polls giving a projection of the outcome will be announced right when polls close, though official results are not expected until early in the week.
Australian Associated Press