Who are the incumbents?

The Right-wing populist Law and Justice Party (PiS) has governed Poland since sweeping to power in 2015.

Mateusz Morawiecki is the prime minister, but party chair and veteran nationalist Jaroslaw Kaczynski has long been widely acknowledged as the real power broker. However, the 77-year old has suggested another four-year term could be his last.

Law and Justice has governed Poland only one other time, as part of a fragile coalition formed in 2005 that collapsed after two years.

At the last election, the party won a straight majority after promising to move the country in a radically different direction.

What are they known for?

Law and Justice has again campaigned with pledges of generous social welfare spending after four years of robust economic growth.

The party argues Poland's rapid economic development since the end of the Cold War has left too many Poles behind, instead primarily serving a narrow elite and foreign interests.

In the build-up to polling day, it has pledged a 78 percent increase in the minimum wage by 2023.

Identity politics has also played a central role in its campaign. Backed by the Catholic church in a country where 86 percent of citizens in a recent poll identified themselves as religious, Law and Justice has made the scaling back of LGBT rights its rallying cry on the campaign trail, brandishing them part of an "un-Polish" cultural liberalism imported from abroad.

That has led to accusations the leadership is stirring up hatred against minority groups. At one Pride march calling for LGBT rights to be protected, protesters were attacked with bottles and stones.

To its critics, Law and Justice has set Poland on a path to a more authoritarian kind of politics with judicial reforms they say make judges subordinate to ministers and with curbs on independent media. Law and Justice insists such changes are needed to clear out remnants of a previous regime that preceding governments had failed to do.

Who are the opposition?

The Civic Coalition is built around the center-Right Civic Platform, which returned to opposition in 2015 after two terms in office under the leadership of the now-outgoing European Council president Donald Tusk.

After a period of soul-searching during which the party struggled to redefine itself in the wake of defeat to the nationalists, it chose Malgorzata Kidawa-Blonska as its candidate for prime minister.

Kidawa-Blonska is a veteran MP and once served as spokesperson for a previous Civic Platform government. She has political heritage, too – one of her great grandfathers was a Polish president, another prime minister.

The Coalition's campaign is centered on a liberal, pan-European platform that seeks close ties with Brussels and calls for "cooperation not quarrels," in reference to a four-year Law and Justice term it argues has stirred up divisions between Poles.

Despite a series of scandals for the incumbents, recent polls put Civic Coalition well behind. Its best chance may come if Law and Justice fails to gain an outright majority, potentially giving it the opportunity to band together a loose group of Left-wing parties that had slumped in the previous election but could now return to parliament.

How has the economy been doing?

Poland's economy has been transformed since the end of the Cold War. Its last recession came in 1992.

Average wages have surged as the economy has trebled in size during that period of transition from a vassal state of the Former Soviet Union to an increasingly influential independent nation and, since 2004, member of the European Union.

Coupled with that sustained period of economic growth after 1992, levels of economic inequality also increased significantly, but since 2004 the country's Gini coefficient – a measure of income distribution – has begun to steadily decline again.

Between 2016 and 2018, GDP growth has accelerated to 4.3 percent and employment has jumped by 2.5 percent.

What are the other issues in the campaign?

Both main parties are framing this election as a pivotal moment for Poland.

With the stakes so high, the environment has been more often a byline than a headline on the campaign trail. But the outcome could have significant consequences for the rest of the EU on this issue.

That is because the incumbents vowed earlier this month to oppose a Brussels plan for carbon neutrality for the bloc by 2050, casting doubt on hopes that all EU states would sign up before December's COP 25 climate summit taking place in Chile.

Law and Justice argues the EU targets would place a disproportionate burden on Poland's coal-reliant economy, and that energy security must pip environmental concerns.

That may prove yet another cause of friction between Brussels and Warsaw, particularly given that incoming European Commission president Ursula von der Leyen says she will make climate change her top priority in office.

While it's odds-on power won't change hands in 2019, there may be stronger opposition domestically than before, with polls suggesting a return to parliament for a coalition of Left-wing parties that have made the environment a central part of their campaign.