Voters in Poland are heading to the polls on Sunday for parliamentary elections after a highly contested campaign that the opposition says will decide the country's democratic standing and place in the EU, 

With the ruling Law and Justice Party (PiS) seeking an unprecedented third term after eight years in power - and the EU keeping a close eye - here's what you need to know about the vote. 

What are people voting on?

Besides choosing the new parliament and the country's senate, Poles will also vote on a referendum, where they will be asked to respond to four questions: do they approve of the privatization of state-owned enterprises; do they want a fence along the Belarus border to be removed; do they want to accept the EU's migrant-relocation scheme; and do they support an increase in the retirement age? But it is the question of political representation that remains most controversial.

Who are the main parties?

Voters have two very different political options to choose from. The first is the ruling PiS party, led by Jarosław Kaczyński, which advocates for greater self-reliance, less influence from the EU, less immigration, and the further reduction of military assistance to Ukraine. 

Their biggest opponent is the Civic Coalition (KO), led by the former national prime minister and the ex-president of the European Council, Donald Tusk. They are advocating for more integration into the EU, unconditional support for Ukraine, and a more liberal social policy, while promising to undo PiS's changes to the judiciary and media. 

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Then there's the Third Way, a center-right paramilitary alliance of Poland 2050 and the Polish Peasant's Party. They want to simplify the tax system and help small businesses. In contrast, the New Left, currently polling at around 10 percent, is focused on labor law reforms, empowering trade unions and gradually introducing a 35-hour working week. There's also the far-right Confederation alliance, which has canvased on a platform of opposing social benefits for Ukrainian refugees and wants Poland to prioritize its own military over arms to Kyiv.

What are the key issues?

For several years now, the opposition has criticized a decline in civil rights and press freedoms brought about by the current government, as well as its strong political influence on the country's judicial system. They say that neither these elections, nor the referendum being held at the same time, are fair, accusing the ruling PiS of deliberately twisting the referendum questions to influence and intimidate the voters. The EU, who regularly clash with PiS over the similar issues, will be closely watching the result.

The issue of Ukraine is also on the table, as PiS recently announced that Poland is not going to supply any more weapons to Ukraine as the country needs to focus on rearming its own military. It was a huge blow to Ukraine, which considered Poland one of its biggest allies and weapons suppliers. The KO vows to overturn that PiS decision if it wins the majority at the elections.

Who is most likely to win?

Just a few days ago, Warsaw saw the largest political rally in its recent history, when hundreds of thousands gathered against the government's policies. Yet, as polls show, there's not enough nationwide support for the KO, as PiS has a significant lead. 

Depending on the opinion poll, the difference between the two ranges from just a few percent in the polls to over 10 points. That difference would most likely exclude a need for a post-election coalition and allow PiS to single-handedly rule Poland for the next four years. The first preliminary results should be known by midnight local time on Sunday, while the full official results are expected on Tuesday morning.

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