The acid test will come fast: the new government must next month come up with over 11 billion euros in extra spending cuts for 2013 and 2014 to keep getting bailout aid, and get the plan approved by parliament.

With an economy which has already narrowed its budget deficit from 15.6 percent of GDP in 2009 to 9.1 last year and is forecast to shrink by another five percent in 2012, that will be a tough task given a parliament that could feature as many as seven small parties opposed to the bailout, including the extreme-right Golden Dawn.

"WILD CARD"

Polling stations will open at 0700 local time (0400 GMT) across Greece and close 12 hours later, with many voters making up their mind at the last minute.

Pollsters say it is impossible to say who the undecided will cast a ballot for as the traditional left-right divide has given way to pro- or anti-bailout lines.

"All our tools are based on a society that does not exist any more," said Costas Panagopoulos, at ALCO pollsters. "We cannot exclude any scenario."

The first indication of the result is expected from about 1830 GMT but it could take many more hours to get the final outcome or even a clear picture under complex electoral system that gives a 50-seat bonus to the first party.

If no party wins outright, as is expected, the president will give the biggest group - expected to be New Democracy - three days to form a government. If it fails, the next largest party gets a chance and so on down the line. If they all fail, new elections would be called in about 20-25 days.

The Greek ballot could well steal the limelight from the likely election on the same day of a Socialist to lead France as president for the first time in 24 years.

"The wild card is Greece, and markets are starting to get nervous about it," said Sassan Ghahramani, CEO of New York-based hedge fund advisers SGH Macro. "We could see peripheral bonds and the euro pressured on Monday."

(Additional reporting by Dina Kyriakidou; Writing by Ingrid Melander, editing by Mike Peacock)