ReutersA Greek orthodox priest prepares to vote in Athens Sunday in Greece's parliamentary elections.Greeks headed to the polling booths Sunday for the third time in less than three years to elect a new government, a vote that could determine the country’s future in the eurozone and reverberate across Europe. According to recent public-opinion polls, Greece’s radical leftist Syriza party was poised to win the general elections, but it wasn’t clear whether its share of the vote would be enough to clinch an outright majority in the legislature. Syriza has been steadily leading in the opinion polls for the past year, while its lead has widened further in the days immediately before Sunday’s vote. The polls show the party garnering between 29.6% and 33.4% of the vote, edging out the incumbent New Democracy party by five to 10 percentage points. The outcome could have lasting repercussions for both Greece and the eurozone. Syriza, which emerged as the main opposition party in mid-2012 at the depths of the nation’s debt crisis, has promised to tear up the austerity and overhaul program that Athens pledged in exchange for a EUR240 billion ($269 billion) bailout from international creditors. Since that deal, Greece has undertaken a broad sweep of revamps and cutbacks that have helped fix its public finances and nudged the economy back to growth following six years of deep recession. Those cutbacks have come at a cost: Some 25% of Greeks remain jobless, while a quarter of households live close to the poverty line. However, Syriza’s promises to roll back many of those overhauls and its demands for debt relief from Greece’s international creditors have also stoked fears of an open clash with eurozone partners that could lead to the country’s exit from the common currency and once again rattle financial markets world-wide. In the past three months, Greece’s financial markets have shed roughly a fifth of their value, while nervous depositors have withdrawn several billions of euros from the country’s banking system. A Syriza victory would also be closely watched by other antiausterity parties in Europe—on the left and the right---that have been gaining ground in the past year. An expanded version of this report appears at WSJ.com