If successful, PM Donald Tusk's Civic Platform would become the first Polish party to win two consecutive terms since the fall of communism in 1989.
Mr Tusk has presided over four years of strong economic growth.
Analysts say turnout will determine the make-up of the governing coalition. Civic Platform is currently allied with the Peasants' Party (PSL).
Opinion polls suggest Civic Platform (PO) is likely to win Sunday's general election.
However low turnouts have traditionally favoured its main rival, Jaroslaw Kaczynski's conservative-nationalist Law and Justice (PiS) party, which has a more loyal core constituency.
"Nothing is prejudged yet, we will be fighting for our coalition to the very end," Foreign Minister Radoslaw Sikorski, also a deputy head of PO, said this week.
Analysts say a low turnout could force the party to seek a less natural partnership with the opposition Democratic Left Alliance (SLD).
'Aspirations'
Mr Tusk has campaigned on Poland's strong growth and has vowed to pursue a steady rapprochement with Russia, despite rows over missile defence and gas pipelines as well as the conduct of an inquiry into a plane crash that killed Poland's president last year.
Poland's relatively large domestic market, which reduces its dependence on exports and EU-funded public sector investments, helped it through the first wave of the financial crisis.
The country has been was the only EU member state to avoid recession and, this year, its economy is forecast to grow by about 4%, the highest rate among the EU's seven largest economies.
But, according to Andrzej Rychard, of the Polish Academy of Sciences, such economic success might not translate into votes at the ballot box.
"Poles are not comparing themselves continuously with other nations - they are comparing themselves with their aspirations and expectations," he told the BBC.