Campaigning has reached its climax in Greece for Sunday's parliamentary elections, with public opinion polls predicting a very close race between the two main parties. With only a couple of days to go in what has been a whirlwind month of campaigning, the main contenders for Greece's parliamentary elections are pulling out all the stops.

The Sunday election is mainly a race between the ruling Socialist Party, known as PASOK, and the conservative opposition called New Democracy. The two parties are staging massive rallies in downtown Athens to get out every vote in what many analysts are suggesting could be a close race.

As recently as January, the government seemed to have no chance of re-election. Polls showed that voters, tired of a party that has been in power for 19 of the past 22 years, were eager for a change.

The same surveys showed New Democracy surging ahead of its long-time rival by up to 10 points. Part of the reason was its leader Konstantinos Karamanlis, a nephew of former Greek President Constantine Karamanlis.

Then PASOK came up with a heavyweight political name of its own. George Papandreou, son of former Prime Minster Andreas Papandreou, took the helm of the party, as Costas Simitis stepped down. Mr. Papandreou created some political momentum that began to take back some of the political ground lost to New Democracy.

That comeback appeared to stall last week, when Mr. Papandreou was generally seen to have performed badly at a pre-election debate, while Mr. Karamanlis did well.

But the gap between the two parties has narrowed to only a few percentage points, and many commentators, like Grigoris Nikolopoulos, of Vima Newspaper, believe that watching the results come in late Sunday will be an exciting time.

"I believe that it will be a thriller on Sunday night," he said. "Polls show that the New Democracy will win, but PASOK is not out of the game. What happened at the last election was that New Democracy voters were out on the streets celebrating, and at about 11 o'clock they went back home and PASOK voters went out on the streets celebrating."

The key factor in the poll is set to be the huge number of swing voters, who have not yet made up their minds. Mr. Nikolopoulos says up to 20 percent of Greece's 10 million eligible voters will decide who to vote for in the final hours before they cast their ballots.

"It is about 18 to 20 percent at the moment which are considered as undecided," he said. "We do not know from now what will happen with the undecided voters. Nobody will know until Monday morning."

With so many voters still up for grabs, PASOK and New Democracy are trying to secure key constituencies that could swing the election in their favor.

Among the key promises made this week, George Papandreou said PASOK would double farmers' pensions, which prompted jibes of checkbook electioneering from the opposition.

Meanwhile, New Democracy has attacked what it claims is a bloated administration, rife with cronyism, and has vowed to dismiss as many as 10,000 government employees on its very first day in office.

The two parties are have also increased their rhetoric. Mr. Papandreou has suggested that New Democracy has ties to extreme right-wingers who, "burn books instead of reading them."

But on several key policy issues the two parties have drifted towards the center, with little difference between their positions. Gone are the days of saber-rattling against Turkey, the traditional Greek enemy. Now, both main parties promise a détente with Turkey and reduced military spending.

Both sides have also agreed not to make the Olympic Games in Athens in August a subject of the campaign. But with only five months to go before the Games, and with many venues yet to be completed, whoever is elected will face an enormous task to finish preparations for the globe's flagship sporting event.