Poles vote in a parliamentary election on Sunday which the opposition says will determine the country's democratic standing and place in the European Union, after a bitterly contested campaign dominated by issues of sovereignty and security.
Since coming to power in 2015, the nationalist Law and Justice (PiS) party has repeatedly clashed with the EU over reforms that critics say have politicised the judicial system and turned state-owned media into a propaganda outlet.
The opposition says the vote could be the last chance to halt what it sees as Poland's drift away from the European mainstream and towards a semi-authoritarian system.
"I know... that they are planning systematically, in cold blood, to take Poland out of the European Union," Donald Tusk, leader of the largest opposition grouping Civic Coalition (KO) told supporters.
PiS denies any such plan.
War in neighbouring Ukraine
With war raging in neighbouring Ukraine and a migrant crisis brewing, national security and immigration have featured heavily in a campaign that was also marked by a souring of relations with Kyiv over Poland's ban on grain imports.
PiS casts the election as a choice between an opposition that is beholden to foreign interests, particularly those of Germany, and soft on migration, and a government that will defend Poland's sovereignty and borders.
"Für Deutschland, that is, for Germany. He repeated these words very often," PiS leader Jaroslaw Kaczynski told a campaign rally, hammering home his party's message that Tusk is a German stooge.
"He certainly would not have protected us from the flood of Ukrainian grain, because for that you had to have courage - to oppose Germany, to oppose the European Union."
PiS has emphasised the effect its social benefit programmes and minimum wage increases have had on living standards, saying the return of Mr Tusk, who was prime minister from 2007-2014 before serving as European Council president, would jeopardise this.
Mr Tusk pledged not to end any of the programmes and has said an increase in child benefits should be implemented sooner.
The KO leader said he would unblock billions in funds withheld by the EU over rule-of-law concerns on day one after winning the election.
However, EU officials say it is unlikely to be so simple as changes to any laws pushed through by PiS would still require the signature of president Andrzej Duda, a PiS ally.
Uncertainty
A referendum is also being held on election day. PiS says it aims to ensure the will of the people is respected on four issues: privatisation of state companies, raising the retirement age, a fence on the Belarus border, and accepting migrants under an EU deal.
However, the opposition says that PiS is misusing public funds for a campaign exercise designed to energise its supporters and demonise opponents with loaded questions.
Opinion polls suggest that PiS will remain the largest party in parliament but may fall short of a majority.
An inconclusive result could lead to legislative paralysis in a frontline Nato member state of crucial logistical importance to the alliance's efforts to aid Ukraine.
A PiS administration that relied on the votes of the far-right Confederation party, which has sought to harness a rise in anti-Ukrainian sentiment among some voters, could be much less inclined to help Kyiv, analysts say.
Coalitions
Key to the election's final outcome will be the fortunes of the centre-right Third Way coalition.
Coalitions need at least 8 per cent of the vote to enter parliament, and some polls have shown Third Way perilously close to this threshold. Should it fail to enter parliament, the opposition's hopes of forming a government would be dashed.
However, Third Way says it is confident it will get the votes required and one of its leaders, Szymon Holownia, said he was "absolutely not afraid" after a recent survey put the coalition on 7.6 per cent.
