In an election fought over the punishing austerity package demanded by international lenders as the price of keeping Greece from bankruptcy, opinion polls showed the radical leftist Syriza party, which wants to scrap the deal, running neck and neck with the conservative New Democracy, which broadly backs it.
The European Union and International Monetary Fund have insisted that the conditions of the €130bn bailout accord agreed in March must be accepted fully by a new government or funds will be cut off, driving Greece into bankruptcy.
All parties say they will keep Greece in the single currency, but Syriza leader Alexis Tsipras believes the agreement can be renegotiated without Greece having to leave, betting that European leaders cannot afford the turmoil that would be unleashed by cutting a member of the eurozone loose.
On the right, establishment heir and New Democracy leader Antonis Samaras says rejection of the EU/IMF bailout would mean a return to the drachma and even greater calamity, although he, too, wants to renegotiate some aspects of the package.
Opinion polls show Greeks, weary after five years of deep recession, overwhelmingly favour remaining in the euro, but there is bitter anger over repeated rounds of tax hikes, slashed spending and sharp cuts in wages.