MOSCOW (AP) _ The growing likelihood that Boris Yeltsin may not serve out his second term means Russia could soon face another tumultuous election over who will lead the vast, chaotic nation into the next century.

The very fate of democracy hung in the balance in this past summer's presidential election. Some voters feared election violence, massive cheating, even a coup d'etat.

But the election went off peacefully, strengthening the country's young democracy. All the likely candidates to replace Yeltsin want to do it through the ballot box.

Most Russians don't want another election so soon, but they seem confident that another leader could be elected and don't fear upheaval _ no small feat in a country that has just emerged from centuries of authoritarian rule.

Despite his need for heart surgery after at least two heart attacks, only death is likely to end Yeltsin's grip on power. The president has ruled out stepping down and there appears no way to force him out.

The constitution says the president should step down if incapacitated by sickness, but the wording is vague and nobody has the authority to determine if the president can no longer function.

Yeltsin suffered two heart attacks in 1995, but refused to give up power even though he was hospitalized for months. If Yeltsin is incapacitated, top aides who depend on him for their posts are likely to minimize the seriousness of the situation to keep him in power.

If Yeltsin were to die or resign, the constitution says elections must be held within three months, with the prime minister heading an interim government. Russia does not have a vice president.

Elections in the next year or so likely would be a replay of this summer's contest when Yeltsin defeated the Communist candidate and won a second term.

Yeltsin won re-election in July despite widespread unpopularity. Many Russians think he has been a shoddy leader who mishandled democratic reform and tolerated corruption. But they reluctantly backed him rather than his Communist rival, Gennady Zyuganov, who advocated a return to the iron control of the Soviet era.

Given the strong anti-Communist vote, the real contest in a new election likely would be over who becomes the main pro-reform candidate.

Alexander Lebed, the former general who is head of the security council, would be a strong candidate. He finished third this summer and has made no secret of his ambition to replace Yeltsin. He recently pushed through an agreement ending the unpopular Chechen war, boosting his standing, and has been softening his strong nationalist stance to appeal to moderates.

Lebed is respected by many Russians for his personal integrity and no-nonsense pragmatic approach. He is seen by many voters as a political maverick who has not sold out to the political establishment.

Prime Minister Viktor Chernomyrdin is likely to run, counting on the backing and money of the political establishment and business leaders. But Chernomyrdin is not popular with voters, who see him as a gray bureaucrat, and his party has done poorly in parliamentary elections.

But Chernomyrdin might enjoy a strong advantage if he could mobilize much of the government's resources behind his candidacy. Yeltsin's control of state resources, ranging from TV networks to local aid programs, played a major part in his re-election.

The Communists have talked of moderating their position to widen their support, but the party is dominated by hard-liners who oppose compromise. Their coalition of leftists and nationalists could tear itself apart over a new election, especially if there is a strong internal challenge to Zyuganov, who was seen as moderate by many in the party.

A major challenge could come from Moscow mayor Yuri Luzhkov, who did not run in the last election. Extremely popular in Moscow for his vigorous rejuvenation of the capital, Luzhkov could appeal to many voters as a new face, unsullied by close ties with the Kremlin and having a strong record of making peoples' lives better.

Among holdovers from the last election, liberal Grigory Yavlinsky would also be likely to run, again offering himself as a young, dynamic reformer. Ultranationalist Vladimir Zhirinovsky would probably run again with calls to smash Russia's enemies, even though his support has been declining steadily.

If there is not an election in the next year or two, other candidates are likely to appear, but most Russians want to continue with democratic reforms despite the pain of the transition from Communism to a market system.

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EDITOR'S NOTE: Barry Renfrew is Moscow bureau chief for The Associated Press.