PORT-AU-PRINCE, HAITI, DEC. 13 -- Just a few years ago, the Rev. Jean-Bertrand Aristide brandished a machete in the pulpit and vowed in fiery Creole to lead a rampage against the army, the Duvalierists, and mulatto and white elites.

Just a few months ago, in New York, he reaffirmed his prescription for Haiti: "Revolution, not elections!" he chanted in a speech to supporters.

But in a sudden reversal that has electrified Haitian politics -- and alarmed many in the business community, traditional political parties and embassies, Aristide announced in October that he was a candidate for president.

"We are the flood," his supporters cry, that will sweep Haiti, rinsing away all that is corrupt, all that is dirty, all that stands for the 29-year Duvalier dictatorship whose lieutenants have lingered even though Jean-Claude "Baby Doc" Duvalier fled into exile in February 1986.

"He is the only credible anti-Macoute candidate," said a European diplomat here, referring to the fearsome Duvalierist militia known as the Ton-tons Macoutes.

"It's not that the Macoutes want to return to power; they don't want to yield it," the diplomat said.

With his 11th-hour declaration, the 37-year-old Roman Catholic priest, who was expelled from the Salesian order in 1988 for using the pulpit to promote class warfare, became the apparent favorite in what had been a sluggish electoral campaign. He could, he has said in his campaign, "stay in my room and sleep" through the elections Sunday and still win handily.

The winner will succeed the current provisional president, Ertha Pascal-Trouillot, on Feb. 7.

Opinions vary on whether Aristide has the backing to win an absolute majority -- and avoid a runoff -- in the balloting against 10 other candidates.

Candidate Marc Bazin, 58, a U.S.-style moderate with a World Bank resume, bulging campaign coffers and a penchant for smart blue suits, is said to be well organized in the countryside, where more than half of Haiti's 6 million people live.

Bazin was a leading candidate in Haiti's last free elections on Nov. 29, 1987. That first free balloting in 30 years was suspended when thugs loyal to the Duvaliers shot or hacked to death 34 people in line to vote as army troops looked on.

This year, the threat of reactionary violence -- especially in response to Aristide's vow to call to account Haiti's traditional rulers -- has hung over the campaign.

The army is seen as critical for keeping the vote nonviolent, and soldiers have provided security at some of Aristide's public appearances. But many observers remain skeptical that the army will remain neutral if Aristide seems set to take power.

On Dec. 5, just after Aristide had left a rally near the capital, a grenade exploded and shots rang out, killing seven and wounding 57, including many children, in the crowd. Army security men were not on the scene, according to witnesses.

The attack, widely blamed on Duvalierists, seemed intended to intimidate Aristide's partisans. But the number of incidents has been minuscule compared to the 1987 campaign, when bodies turned up on the capital's streets every day.

Aristide and many other Haitians blamed the Dec. 5 attack on the Macoutes and called for the arrest of the self-avowed Macoute leader, Roger Lafontant.

Lafontant, who returned to Haiti from exile in July, proclaimed himself a presidential candidate, only to be disqualified by the electoral council. In a sign of the military's sympathy for Lafontant and other stalwarts of the Duvalier regime, the army has refused to honor an arrest warrant charging him with being a threat to national security while serving as interior minister in the mid-1980s. He was widely accused of torture at the time.

Calling Aristide an "ultra-Communist," Lafontant vowed that "we will do everything to prevent" him from winning. He accused Aristide of sponsoring the anti-Duvalierist violence that followed Jean-Claude Duvalier's departure, and that has recurred from time to time, and said Aristide "will get justice, too."

To throngs of supporters in the rotting, rat-infested slums of this capital, Aristide is more than a radical priest with a leftist agenda and a flair for oratorical pyrotechnics.

To them, he is a hero. In Haitian Creole, he is Titid, or "tiny Aristide," who miraculously survived three assassination attempts as dozens died around him. A diplomat's housekeeper swears that Aristide escaped a hail of bullets and a devastating fire at his church, St. Jean Bosco, in 1988 by turning himself into a dog and jumping out the window.

These days, Aristide takes more prosaic precautions, like sleeping in different houses at night. He is widely beloved for having stood up to the Duvalier regime in his sermons and for challenging the Ton-tons Macoutes as other politicians spoke of national reconciliation.

For followers, Aristide has become a symbol of the change that most Haitians expected -- but have not seen -- when Duvalier fled.

In the campaign, Aristide has cooled his rhetoric while stressing in sometimes messianic terms that his is the voice of the people, that his cause is the suffering of the poor, that his candidacy is at the masses' behest.

While he declares readiness to quit the priesthood for politics, his message remains a variation on liberation theology -- the Catholic Church movement to champion the plight of the poor.

But any suggestion that his drive for power could be stopped, either by political violence or a rival candidate, draws an ominous response. If the people's aspirations are denied, he said this week, "I cannot say I will be able to control the situation."

Many Haitian businessmen, traditional politicians and foreign diplomats are concerned that Aristide, who has discounted foreign aid, would frighten off potential aid donors.

They note that he has only recently refrained from xenophobic public statements -- an extreme nationalism shared by the Duvalierists that has been a part of the Haitian political tradition for more than 200 years. For two years he refused even to speak with U.S. officials in Haiti, and he also remains leery of the French, who were the colonial power.

After Duvalierist acts of violence in the past, Aristide has accused the United States of complicity. He also has accused Washington of backing the Duvaliers, seeking to reinforce Haiti's dependence on U.S. imports and dumping cheap commodities on the Haitian market to drive local producers out of business.

Several diplomats expressed particular worry about Aristide's confidants. They include Ben Dupuy, the radical editor of Haiti Progres, a New York newspaper for Haitians; Gerard Pierre-Charles, a respected Communist scholar, and Antoine Izmerry, a virulently anti-American businessman who has financed perhaps a quarter of Aristide's low-budget campaign.

Half of Aristide's campaign funds, which amount to less than $500,000, are said to have come from Haitian exile groups in the United States, where at least 800,000 Haitians live.