Greece's Syriza heads pre-election polls, but lead unclear

By Renee Maltezou and Karolina Tagaris ATHENS (Reuters) - Opinion polls on Friday put the leftist Syriza party of former Greek prime minister Alexis Tsipras ahead by margins ranging from wafer-thin to its widest yet as elections draw near. It and conservative rival New Democracy have been hard to separate in the run-up to the Sept. 20 ballot. But Friday's ProRata poll in left-leaning daily newspaper Efimerida ton Syndakton put Syriza 5 percentage points clear on 28.5 percent - the biggest lead for either of the two main parties in surveys since Aug. 28. Other pollsters cautioned that it was too early to draw conclusions from the latest data, and three surveys later in the day pegged Syriza's lead at between just 0.2 and 1.0 points. Tsipras and New Democracy leader Vangelis Meimarakis have spent much of their campaigns trying to protect their vote, trading accusations over Greece's economic crisis, migration and institutionalised corruption. They clashed most recently in a largely inconclusive televised seven-party debate on Wednesday, but pollsters say a second TV head-to-head on Monday between just the two of them may influence a significant bloc of undecided voters. Friday's surveys put undecideds at between 8 and 17.5 percent. "There is no clear trend yet in favour of one or the other direction. This ambiguity may end next week or even on the day of the election," said Thomas Gerakis, head of the Marc polling agency. With neither party looking close to winning an outright parliamentary majority, the leaders have also broached the issue of post-election alliances, with Tsipras demurring and Meimarakis sounding more amenable. The New Democracy leader told Reuters in an interview on Thursday that he would try to team up with Syriza if his party placed first, and turn to other pro-European groups if that approach was rejected. Syriza forced the election last month when Tsipras resigned as prime minister, hoping to end a party rebellion over Greece's new bailout deal and trade on his then greater popularity by returning to power with a clear majority. (Additional reporting by Michele Kambas; writing by John Stonestreet; editing by Andrew Roche)