With a somber, last-minute warning from Greece's elder statesman about "uncertainty and confusion ahead," voters prepared to cast their ballots Sunday in an election that is too close to call and likely to produce an unstable government.

Breaking self-imposed silence for the first time since he resigned as president March 10 in a chain of events that prompted these elections, Constantine Karamanlis warned Greeks that they have "no excuse" if their votes "lead our country into new adventures."

His oracular statement -- widely interpreted as favoring Constantine Mitsotakis' center-right New Democracy party over the incumbent Socialists of Prime Minister Andreas Papandreou -- was made just before the boisterous, three-week campaign ended at midnight Friday.

So up in the air is the outcome that neither major party may emerge with a majority in the 300-seat parliament.

In that eventuality, the pro-Moscow and Eurocommunist parties could hold the balance of power by supporting a weak Socialist government that few analysts believe would last more than a few months before new elections would have to be called.

Papandreou's Panhellenic Socialist Movement, known as Pasok, has fought what observers have described as a defensive, unfocused and often vulgar campaign, trying to hold onto centrist and Communist support won in 1981, when Greeks voted in their first noncommunist, left-wing government.

Although professional consultants expect the two big parties to share as much as 82 to 85 percent of the vote, even Pasok officials concede that they are unlikely to come close to the 48 percent that gave them 174 seats in 1981.

Analysts argued that Pasok's best chance lies in rural areas -- where farmers are pleased with increased subsidies from the European Community -- now that urban Greeks, roughly a third of the electorate, appear to be swinging back to New Democracy.

Pasok officials say they believe they must win a minimum of 156 seats not to be beholden to the Communists, who have attacked Papandreou as much as Mitsotakis during the campaign. If Pasok is defeated, some Greek analysts believe that Papandreou's organization -- a loosely affiliated "movement" of centrists through leftists -- could break and dissolve.

Nor is a New Democracy victory thought likely to be more than razor thin. Many Greeks and diplomats say they fear that such an outcome could provoke street violence and strikes if Pasok and the Communists are unable to accept defeat graciously.

The electorate's built-in natural left-wing majority is such that one analyst jokingly warned that the center-right would need to win 180 seats -- a mathematical impossibility -- to rule smoothly.

"It's likely the elections will not solve any problems," a western analyst remarked, "and only raise new ones."

Recalling post-World War II history, marred by civil war, right-wing repression, political instability and military dictatorship, he said, "Greek politics seem to bear out Murphy's Law and invariably produce the worst possible results. Let's hope I'm proved wrong."

New Democracy and Pasok have accused each other of seeking to end democratic institutions during the campaign, which has polarized Greek politics further.

But, unlike the 1981 campaign, foreign policy has played a minor role this time.

Then, Papandreou played to Greek nationalism by threatening to close down U.S. military bases and end Greek membership in the European Community.

He has dropped both threats, at least temporarily.

Whoever wins Sunday will be faced by increasingly serious economic problems -- even if both major parties fail to honor their extravagant election promises.

Breaking with both the socialist and old conservative tradition of state intervention in the economy, Mitsotakis added "liberal" to his party's official title in an attempt to attract centrists. He stumped for less government, lowering taxes and allowing market forces to straighten out the anemic economy.

Papandreou, who swept to power last time with a masterful American-style campaign promising allaghi or change, this time has found himself in the uncomfortable position of the incumbent defending a spotty record.

Pasok appeared to be caught so much on the defensive that the party press indulged in a mudslinging campaign, variously accusing war hero Mitsotakis of being a Nazi collaborator and of colluding with the discredited former king Constantine, who now lives in exile in London.

As a campaign crowd in Patras chanted, "The friend of the SS will die," Papandreou did nothing to stop them and indeed referred to Mitsotakis as "the friend of the SS, as you call him."

On another occasion, the prime minister described his adversary as "an outcast of society, an agent for foreign interests, a wandering Jew."

Even some Pasok officials privately expressed their disapproval of such rhetoric.

As is traditional in Greek campaigns, there were no public debates between competing politicians. All major parties preferred large rallies with hundreds of thousands of followers crowded into spectacular finales in Athens' Constitution Square, shooting off firecrackers, blowing boat horns, shouting themselves hoarse -- and drowning out the candidates' speeches. "We came here to show our support," one Mitsotakis supporter remarked the other evening, "not to listen."