By Justyna Pawlak and Pawel Florkiewicz
WARSAW (Reuters) - Poles vote in an election on Sunday that could end nearly a decade of economic and political stability in the country of 38 million, bringing to power a conservative, eurosceptic party whose policies diverge from many of Poland's European allies.
If opinion polls are correct, the ruling Civic Platform (PO), a pro-market, centrist grouping in power for the past eight years, will lose to the conservative Law and Justice opposition party (PiS), run by the twin brother of late president Lech Kaczynski, Jaroslaw.
Most polls show PiS as the frontrunner on more than 30 percent, while PO is second with just over 20 percent. Several small parties are also running, spanning the political spectrum from ultra-right to liberal and extreme left.
Distrustful of the European Union and an advocate of a strong NATO hand in dealing with Moscow, PiS opposes joining the 'euro zone' in the near future, promises more welfare spending on the poor and wants banks subject to new taxation.
It also opposes the relocation of migrants from the Middle East to Poland, arguing they could threaten Poland's Catholic way of life - raising the prospect of tensions with the EU on the issue.
On the campaign trail, Kaczynski and other PiS leaders have sought to tap into anger that the economic success is not more evenly shared out and into nationalist sentiment fanned by immigration fears, particularly among young voters.
"If (PO) maintains power, if we don't manage to take it from them, things will be much worse than before. You may say things cannot get worse. Things can always get worse," Kaczynski told supporters during a rally in Lublin, some 80 km (50 miles) from the Ukraine border.
Poland has seen its economy expand by nearly 50 percent in the last decade and is the only EU member not to experience recession after the 2008 financial crisis. But pockets of poverty and stagnation remain, particularly in the east.
"There is a broader phenomenon of a return to national, religious, community values being seen all across Europe," said political analyst Aleksander Smolar.
"PiS uses clear ... language in this respect."
Kaczynski was accused by some Polish media this month of fanning racism when he said migrants fleeing war in the Middle East and Africa may bring new diseases and parasites to Poland.
PO Prime Minister Ewa Kopacz later quipped Kaczynski, a known cat lover, wasn't too worried to own cats even though they can carry diseases dangerous to people.
"There are many diseases that come from animals, but at the same time that doesn't stop (Kaczynski) from having a cat," she said.
PiS's advocacy of a robust Western approach towards Russia following Moscow's 2014 annexation of the Crimean peninsula in Ukraine might also complicate any future bridge-building between the EU and Russia.
Several new parties are running on anti-establishment platforms, supported largely by young voters.
Among them, Kukiz'15, a grouping run by former Polish rock star Pawel Kukiz, which wants to tax "bank gangsters" and says Poland is a "colony of foreign governments". Kukiz ran in a presidential election in May, winning a shock 21 percent.
"I hope we enter parliament in such numbers that it will allow us to make a crack in the system, allowing the citizens, the nation to win back control over the state, which has been taken away from them," Kukiz told a campaign rally.
The smattering of fringe parties in the election means PiS, even if it wins, will likely have to seek coalition partners to rule, raising the possibility of extended talks in the weeks after the vote.
It also leaves room for PO to retain its hold on power, if PiS fails to form a functioning majority in parliament and the centrists secure the support of leftist groupings such as United Left (ZL) or liberal Nowoczesna.
Polls open at 7 a.m. local time (0600 GMT) and close at 9 p.m., (2000 GMT). Exit polls will be available immediately after voting ends.
(Additional reporting by Wiktor Szary; Writing by Justyna Pawlak; Editing by Richard Balmforth)