BELGRADE, DEC. 8 -- The survival of Yugoslavia may well be at stake as voters in this country's largest and most vehemently nationalistic republic go to the polls Sunday in the first free election in half a century.

The vote here in Serbia, and in the smaller republic of Montenegro, concludes a revolutionary round of elections in the six republics of this ethnically fractured nation. So far, voters have dumped the old Communist system and opted for a pugnacious brand of nationalism.

Newly elected leaders in the two northern republics -- Yugoslavia's richest and most Westernized -- have been demanding autonomy from the federal government in Belgrade. The two, Slovenia and Croatia, are threatening to secede from Yugoslavia if they cannot negotiate a fundamental weakening in federal power.

The U.S. Central Intelligence Agency, in a report leaked in Washington last month, predicted that Yugoslavia will split apart within 18 months and that civil war is likely. Politicians and diplomats here say that chances of the CIA scenario coming true depend in large measure on what Serbian voters decide Sunday.

The election pits the Communist (recently renamed Socialist) regime of Serbian President Slobodan Milosevic against more than 50 mostly anti-Communist opposition parties. The presidency, an office with near-dictatorial power, and all 250 seats in the legislature are up for grabs.

The election here has developed as a far more emotional affair than political races elsewhere in Eastern Europe. Economic reform, a subject of heated debate in most of the region, is a side issue in Serbia.

At center stage is nationalism.

Candidates who refuse to emphasize above all that Serbia is a great nation -- a popular campaign song is "Whoever Says Serbia Is Small Is Lying" -- are not considered serious contenders.

Milosevic, a career Communist who now campaigns in a sheltering cocoon spun by the state press that he controls, first played the nationalist card three years ago.

Serbs, of whom there are about 8 million, have long felt like second-class Yugoslavs. The ruling strategy of Marshal Tito, from the end of World War II until his death in 1980, was to keep the Serbs from asserting themselves as the largest ethnic group in this country of 23 million. Milosevic broke Tito's spell on a celebrated night in 1987 when he told a crowd of Serbs, "Nobody will beat you again."

Since then, as he has consolidated power in a regime that is characterized by his political critics as Stalinist, Milosevic has become a Serbian folk hero.

At a rally this week, middle-aged Serbian women danced in circles holding aloft his photographs. Every few seconds, they pressed their lips to his. "With you we are going to defeat all the enemies," said a campaign banner at the rally.

Enemies are what Milosevic has specialized in manufacturing. Western governments consider him the individual most responsible for pushing Yugoslavia toward civil war.

His Serb-first policies have turned Kosovo, a Serbian province with an ethnic Albanian majority, into an armed camp. Amid international charges of systematic human rights abuses, the once-autonomous local government of Kosovo has been dismantled and replaced by Serbs who report to Milosevic.

Without evidence, the press that Milosevic controls has accused the governments of Croatia and Slovenia of running guns to Albanians in Kosovo. Milosevic has imposed Serbian duties on goods manufactured in the northern republics. He has said that he will only consent to Yugoslavia becoming a loose alliance of independent states if a large part of Croatia is ceded to Serbia.

By wrapping himself in Serbian nationalism, Milosevic found a talisman to ward off the anti-Communist sentiment that infected all of Eastern Europe in the past two years. Sunday's election will show whether that talisman can continue to work.

To Milosevic's considerable annoyance, however, a new folk hero has elbowed his way into Serbia's presidential race.

In a campaign that seems as much performance art as politics, a novelist named Vuk (Serbian for Wolf) Draskovic has staked out turf even more nationalistic than that held by his Communist opponent.

Milosevic has attacked Draskovic as a throwback to "completely dark forces" that want "to return Serbia to the past and drag it down into chaos."

Opinion polls, although not considered very reliable, show Draskovic running a close second and gaining ground on the president. Polls show that his Serbian Renewal Movement may win the largest number of seats in Parliament.

Draskovic, 44, has cultivated the look of a turn-of-the-century Serbian patriot. A tall man with dark, deep-set eyes, he has a flowing black beard and long, unkempt hair. He often wears a cape.

With a public image that is part Rasputin, part rock star, Draskovic is probably the most physically imposing and theatrically gifted of all the major political figures to emerge this year in Eastern Europe.

On the stump, where he is usually flanked by large paintings of Serbian kings, he portrays his campaign against Milosevic as a war between "the cross and the red star," between the wholesome values of the Serbian Orthodox Church and the "evil" of communism. When drawing these battle lines in his speeches, Draskovic grandly touches his hand to his forehead and gives the sign of the cross.

Draskovic seems to revel in histrionics. On Thursday in Belgrade, as he stood bareheaded on an outdoor platform in a driving snowstorm at dusk, Draskovic said he just heard that his political enemies were out to get him:

"There is a terrorist troika founded by the leadership of the Socialist Party to liquidate me. They {his advisers} want me to wear a bulletproof vest. Those cowards! I am not wearing anything."

Draskovic made his name in Serbia in the early 1980s with a series of rabidly nationalistic best-selling novels. A recurring theme in the books is how innocent Serbs were betrayed, abused and murdered by Croats and Moslems during World War II. It was after the books made him famous (and relatively wealthy) that Draskovic -- a former Communist who served as a speechwriter for a one-time Yugoslav prime minister -- grew his beard and long hair.

As recently as two months ago, Draskovic was offering a number of explosively simple solutions to Serbian worries.

In Kosovo, which Serbs regard as their traditional homeland but where nine of 10 residents are now ethnic Albanians, Draskovic said he had a "seven-day" solution. He proposed that Albanians either sign a Serbian loyalty oath or get out. If the 1.7 million Albanians who live there did not want to do either, Draskovic said the army would force them out.

Draskovic also has said that much of Croatia belongs by historical right to Serbia. He has argued that millions of Croats must be relocated for historical justice to be served.

As his campaign has gathered support, however, Draskovic has dramatically moderated his views. His party has splintered, shedding itself of the most militant Croat-hating factions while picking up a number of advisers from the University of Belgrade.

This week Draskovic promised something that Milosevic has never agreed to. He said that as president he would be willing to talk with elected leaders from Croatia and Slovenia, as well as with Albanian leaders from Kosovo, about the political future of the country. Should Milosevic win and refuse to hold such talks, as he has repeatedly vowed, many fear the country would surely break apart.

"Regardless of whether Yugoslavia continues to exist or not, Serbs and Croats will have to live together peacefully as neighbors," Draskovic said.

"Vuk has toned down a great deal. He is willing to accept people from other parties into his government. He is not after revenge," says Vladata Jankovic, a leader of the Democratic Party of Serbia, a party of professionals and technocrats that emphasizes the need for economic reform. The Democrats say they will gladly serve in a government headed by Draskovic.

Despite his wild-eyed appearance and his previously blood-curdling rhetoric, Draskovic is now viewed by most opposition politicians, by Western governments and by elected leaders in Croatia and Slovenia as a more palatable Serbian president than Milosevic.

"He is preferable to Western interests. Vuk will dismantle the police state. He has thrown a bone to the other nationalities," said a Western diplomat here. "If Milosevic wins big, the CIA scenario {about the breakup of Yugoslavia and civil war} is going to play. I don't see how the northern republics could stay in Yugoslavia."