"Now Poles will be able to chose if they want a modernised, growing Poland or a Poland ruled by a network of oligarchs," prime minister Kaczynski told a news conference after the vote.
Kaczynski wants a clear mandate for social policies to support families who have not benefited from an economic boom and a programme to rid the establishment of what he calls a corrupt post-communist elite.
But many businesses hope for a strong showing by the Civic Platform (PO), which wants to speed up change in central Europe's biggest economy and move more quickly to adopt the Euro.
Donald Tusk, the Civic Platform leader, said: "Only an early election can bring a better government to this country."
After trailing for months in opinion polls, the Kaczynskis' ruling Law and Justice party (PiS) has started to swing back to favour.
But, if the party wins the most seats, it may still struggle to form a coalition because the Kaczynskis have alienated so many potential partners.
Neither party appears set to win enough parliamentary seats to be able to easily form a coalition.
One opinion poll published on Friday gave Civic Platform a 3-point lead. Another put the ruling party two points ahead.
A research note from Gyorgy Kovacs of UBS bank said: "We expect that financial markets would react positively if business friendly PO formed the next government, while a PiS led government would basically imply a continuation of the current track."
Despite political turbulence, Poland's economy has thrived, growing at its fastest rate for a decade with gross domestic product rising at about 7 per cent a year.
But the opposition has strongly condemned the Kaczynskis for dividing Poles with their determination to examine the communist past of 700,000 citizens.
They also accuse the Kaczynskis of undermining Poland's image abroad with their constant quarrels with the European Union and neighbour Germany in particular.