Athens, Greece ? They are rivals with much in common: Both come from famous Greek political families and talk about remolding the country in the image of richer and more dynamic European Union partners.

Voters will decide Sunday which gets the task of leading the country when it comes under the world spotlight of this summer’s Olympic Games — and then afterward, when the government must pay the event’s staggering bills.

The choice is whether to return the opposition conservatives, led by Costas Caramanlis, to power for the first time in a decade or hand George Papandreou’s Socialists an unprecedented fourth consecutive term in office.

The parties are running close and spent the final days before parliament elections hunting for every possible vote.

The wide net shows a fundamental shift in Greek politics. In past campaigns, the two main parties — the Socialists and the New Democracy — could count on their core of supporters with very few defections to the other side.

Now, the lines have blurred, making for unpredictable politics.

Caramanlis sticks to promises of smaller government, less bureaucracy and fewer taxes. But he can also take pages from the Socialists — calling for expanded social welfare programs and higher pensions.

Papandreou can sound rock solid conservative with appeals that were once unthinkable for the party founded by his father 30 years ago. Among Papandreou’s plans are speedier privatizations of state enterprises and lower corporate taxes.

“Voters, and especially undecided voters, feel that the two big parties no longer have any differences,” said political analyst Yiannis Loulis. “Greeks have become very pragmatic.”

The most recent opinion polls showed Caramanlis holding a 3.5 percentage point advantage over Papandreou. Victory would bring New Democracy to power for the first time since 1993 and signal another snub in Europe for established socialist governments.

Caramanlis, 47, ended his pre-election campaign Thursday with a rally in central Athens. Papandreou planned to finish the Socialist campaign with a similar gathering today.

With the Olympics only five months away, much is at stake.

There are worries that many Olympic projects — including a roof for the showcase Olympic stadium — may not be finished in time for the Aug. 13-29 games.