European leaders urged Greece to reject radical leftists who threaten to tear up the terms of a bailout deal should they win an election on Sunday, a result that would send shockwaves through global financial markets.
Riding a wave of anger to rise from obscurity to contender for power, leftist SYRIZA leader Alexis Tsipras, 37, promises to reject the punishing terms of the 130 billion euro ($163.75 billion) bailout if he wins the nail-biter vote on Sunday.
On the right, establishment heir and New Democracy leader Antonis Samaras, 61, says that would send Greece crashing out of the single currency and condemn it to even greater economic calamity.
With the election set to go down to the wire, European leaders weighed in on Saturday, urging Greeks to vote with their heads.
The bailout will not be renegotiated, warned German Chancellor Angela Merkel, whose country's wealth is vital to shoring up its weaker partners in the bloc.
"That's why it's so important that the Greek elections preferably lead to a result in which those that will form a future government say: 'yes, we will stick to the agreements'," Merkel told a party conference of the Christian Democrats.
Eurogroup head Jean-Claude Juncker said there would be serious consequences if SYRIZA secured victory.
"If the radical left wins - which cannot be ruled out - the consequences for the currency union are unforeseeable," Juncker, head of the group of euro zone finance ministers, told Austrian paper Kurier.
"We will have to speak to any government. I can only warn everyone against leaving the currency union. The internal cohesion of the euro zone would be in danger.
Tsipras says Greece's lenders are bluffing when they threaten to turn off the funds if Athens reneges on the terms of the bailout - tax hikes, job losses and pay cuts that have helped condemn the country to five years of record-breaking recession.
FEARS FOR SPAIN, ITALY
Tsipras says the euro zone will not allow a Greek exit, fearing the pressure it would heap on the far larger economies of Spain, which has already secured a 100-billion-euro rescue for its banks, and Italy, which could be next to seek a bailout.
Italian Prime Minister Mario Monti said he and other European leaders expected a "favorable" outcome.
"I expect, and I have the impression that many European governments expect a vote that is favorable to maintaining a solid relationship between Greece and the rest of Europe, favorable to Greece staying in the euro zone, favorable to the parties that want to stay in," Monti said in Bologna.
Sunday's vote is a re-run of a May 6 election that produced stalemate, when anger at the close-knit and often corrupt political clique that has run Greece for years propelled SYRIZA from the political fringe into second place.
Opinion polls published until a ban two weeks ago put the two parties almost neck and neck. Neither is expected to win outright, leading to coalition talks with smaller parties.
"My heart says I should vote for the left, for all the horrible things these (mainstream) politicians have done to us, but my mind says vote for the right, so that Greece does not leave the euro," said part-time teacher Kostas Manitsas, 28.
The result will dominate a meeting of the Group of 20 world economic powers in Mexico on Monday and Tuesday.
Spanish Prime Minister Mariano Rajoy made a plea for greater political and fiscal union in Europe and urged Greeks to stick to the course.
"Europe has to transmit to the world that the euro is an irreversible project," Rajoy told a political rally on Saturday in San Sebastian.
Greeks say they want to keep the euro, but they do not want the pension, wage and jobs cuts imposed by the bailout package and which have seen living standards plummet and unemployment reach almost 23 percent.
"Tomorrow's vote must not be based on anger but on hope," the liberal left daily Ta Nea implored in an editorial. "It must be based on the Greece of the euro, not the Greece of the drachma."
But some global businesses and banks are already in retreat: Europe's biggest retailer, Carrefour, said on Friday it was selling up in Greece, a day after French bank Credit Agricole moved to take direct control of its Albanian, Bulgarian and Romanian units from its Greek bank Emporiki.
On Saturday, Germany's Biotest appeared to become the first drugmaker to say it was exiting the Greek market in July after its customers there failed to pay outstanding bills of 7 million euros. Others have threatened to do likewise, as the Greek health sector struggles with huge spending cuts.