ATHENS, June 1 (Reuters) - Greece's June 17 national election is being cast as make-or-break for its future in the euro and the currency bloc itself, but if you're looking to opinion polls for guidance, think again.
With a little over two weeks to go and despite the vote's apparently historic importance, polls have thrown up wildly different scenarios of what the outcome might be.
While most polls have given the conservative pro-bailout New Democracy (ND) party a modest lead, other polls have said the radical leftist anti-bailout SYRIZA party is slightly out in front, and some have suggested that support for the two parties is evenly matched.
Although the two leading parties are each backed by only about a quarter of the electorate, Greek election rules give an automatic bonus of 50 seats in the 300-seat parliament to the group that places first, meaning even the slightest edge could play a decisive role in determining who next rules Greece.
"The polls paint a picture of the really tight race we have ahead of us," Dimitris Mavros, head of the MRB pollster, told Reuters. "The differences are so small and nothing is set in stone. You don't know what will happen at the last minute in such a fragile political landscape."
The uncertainty is unsettling markets because the two frontrunners have radically different visions of Greece.
ND favours keeping the euro along with the latest 130-billion-euro bailout from international lenders and the austerity measures that go with it, with a few minor tweaks.
But SYRIZA says it wants to keep the euro but to renegotiate the rescue package in order to water down harsh austerity measures, something the EU opposes and markets fear.
Stefanos Manos, a former finance minister running in the election with a small party said the polls reflected Greeks' own uncertainty at a time of extreme national stress.
"It's not the polls that are all over the place but public opinion that's all over the place, and the polls merely reflect that," he said.
The gap between the two parties in polls has often been no more than the statistical margin of error of around 2.5 percent.
The main reason why the polls have been so contradictory - according to pollsters and politicians - is that the deep financial crisis Greece is living through has cracked its political consensus wide open, creating unprecedented volatility.
"The dividing line in politics has changed. A new line has been created: those who are for and those who are against the bailout," said Costas Panagopoulos, head of the ALCO pollster.
For decades, ever since a group of army generals lost their grip on power in 1974, Greek voters gave their preference to either the socialist PASOK party or the conservative ND party.
But the country's debt crisis and public fury at the chaotic way the two main parties have handled it, changed that.
VOLATILITY
When a May 6 snap parliamentary election was held, SYRIZA burst into the political mainstream, securing second place.
"Six out of ten voters voted for a different party to the one they had voted for two and a half years ago. It was a protest vote," said Panagopoulos. With Greek politics suddenly polarised around a single issue, many people appear to be undecided or changing their minds by the day.
"According to our polls 25 percent will vote for a different party from three weeks ago," Panagopoulos said.
Mavros, head of the MRB pollster, said decisions may not be made until the last minute.
"In the last election, 40 percent decided in the last two weeks and 20 percent decided on the day in the polling booth."
The country's dozen or so pollsters - all private companies commissioned by fee-paying clients - say the polls they conduct are subject to rigorous regulation.
Each poll must include a minimum of 1,000 voters nationwide and the name of the entity that commissioned the poll must be published along with the full list of questions and answers.
Pollsters sometimes come under fire. Many experts believe polls themselves can influence voters, which is why the Greek government bans their publication two weeks ahead of the vote.
"The bottom line is who pays for and orders the poll has quite a bit of impact on what the questions are," Theodore Couloumbis, a political analyst, told Reuters. He said people tended to vote for or against parties they believed had a real chance of winning, which could depend on polls.
A ban on the publication of any new polls enters into force on Saturday. Public prosecutors launched an investigation into news websites that published polls after the cutoff date in the previous election.
On Friday, the conservative Kathimerini daily newspaper, which had just released a poll putting SYRIZA in the lead, published a front page editorial defending its polls.
"Publishing the polls cannot depend on whether or not we like the result," it wrote.
SYRIZA itself has complained about the erratic polling, saying it had concerns about the way surveys were conducted and wanted government checks in place to ensure they were objective. (Writing by Andrew Osborn)