Alexis Tsipras wound up his campaign to be re-elected Greek prime minister by declaring his victory would strike a blow for Europe's left, as final polls Friday gave him a slim lead.
The return of his Syriza party to power after Sunday's vote would deliver "a key message for Europe", Tsipras told thousands of supporters in his last electoral rally in Athens.
"Do we want a Europe of austerity or one of solidarity and democracy? The result (of the vote) will be a key message for Europe," he said.
Flanked by the leader of Spain's anti-establishment Podemos, Pablo Iglesias, and other EU radicals, the charismatic 41-year-old slammed the conservative leaders of Germany and Spain.
"The struggle to change Europe continues," he said, hailing those who are sheltering migrants fleeing war and persecution. But as thousands of mostly young supporters turned out on a hot Athens night for the rally, Tsipras's flamboyant ex-finance minister Yanis Varoufakis said he would be voting for Eurosceptic radicals who have broken away from Syria.
Tsipras, in a white shirt and with his sleeves rolled up, said that on "Sunday we will sweep away the old", an apparent reference to his main rivals for government office, the established conservative New Democracy party led by Vangelis Meimarakis.
The vote would show, he added "if the old system that governed for 40 years is going to return or if we are going to take a step forward.
"The people will say no to this old system of corruption, no to the enshrining of the oligarch establishment."
Tsipras won office in January with 36.3 percent of the vote on an anti-austerity ticket, but then upset supporters in July with a U-turn cash-for-reforms deal with Greece's international creditors despite winning a huge "No" vote in a referendum on the issue.
But even after the broken promises, many voters believe he has their interests at heart - a break with past leaders they perceived as corrupt and linked to powerful interests.
Hard to forecast
"Syriza will not only win Sunday, it will have a mandate to form a strong and stable government... to go ahead with the reforms the country needs," Tsipras said.
Sunday's third vote in Greece in a year was called after Tsipras resigned in August following a rebellion inside Syriza that saw anti-euro hardliners quit to form a new party, stripping the party of a fifth of its MPs.
Hours before a midnight ban on voter surveys, four polls forecast victory for Tsipras over Meimarakis by margins ranging from 0.7 to 3.0 percentage points.
But Greek pollsters called for caution after being burnt in earlier votes, with the gap falling within some of their margins of error.
"It's the first time I've felt unable at this point to make a forecast," political columnist Paschos Mandravelis told AFP. Polling institutes are working "in shifting sands, after seven months of major political upheaval", said Thomas Gerakis at the Marc institute.
Polls show the two main parties garnering between 25 and 30 percent of the vote, with the remaining parties picking up single-digit scores, meaning neither is expected to be able to form a majority government.
At his last campaign rally on Thursday, Meimarakis urged Tsipras to form a coalition government, an offer already rebuffed.
The bushy eye-browed 61-year-old, a former lawyer, has narrowed the gap with Syriza since he took the helm of New Democracy a couple of months ago.
"I voted for Syriza in January, but this time I'm going to vote New Democracy," said a pensioner at the Meimarakis rally who gave his name only as Costa.
As both Syriza and New Democracy have pledged to stick to the new 86-billion-euro ($97-billion) cash-for-reform package, there will be more unpopular austerity on the way whoever ends up in charge.
But in a flurry of interviews, the 41-year-old former premier has defended his decision to put the country above his party, saying that had he refused to agree the three-year bailout, Greece would likely have been ejected from the eurozone.
On Friday, he told Antenna TV that he would "tug the rope" in order to secure relief on Greece's huge national debt from EU creditors in the coming months.