This Sunday was to mark the first time in almost three decades that Chileans would elect a president outside the shadow of their former dictator, Gen. Augusto Pinochet. Under house arrest in London for 15 months, Pinochet had largely drifted off the national radar screen. And although the race pits a former anti-Pinochet dissident against a former Pinochet aide, both candidates spent more time talking about schools and unemployment than what to do with the ailing patriarch.

But in the past 24 hours, all that changed.

The announcement Tuesday that British authorities may release Pinochet because of his frail health has dropped a political bomb on Chileans. It has starkly clarified the historical context of the choices in Sunday's vote--bringing the first socialist to power since Pinochet overthrew Salvador Allende in 1973 or restoring the right wing for the first time since Pinochet stepped down in 1990. But more importantly, it has once again turned Pinochet into a decisive factor for a country that cannot seem to escape his legacy.

"Pinochet never seems to leave us alone. He is always affecting us, always in our lives, no matter what," said Marta Lagos, a Santiago-based political analyst. "With this last-minute decision in London, they've turned our elections into something as dramatic as any opera. I don't think there's any question that Pinochet will now become a key, deciding issue on Sunday."

Which side will benefit, and how it will benefit, remain very much in debate. Ricardo Lagos, 61, a moderate socialist who was among the bravest dissidents during the dictatorship, is now in the fight of his political life against Joaquin Lavin, 46, the most popular candidate the right wing here has fielded.

Lagos's center-left Concertacion coalition has won both presidential elections since Pinochet stepped down, with its Christian Democrat allies in the presidential palace now.

This is expected to be the case again even with the socialist Lagos as the coalition standard-bearer. But Lavin almost ran even with Lagos in the first round of elections last month and, according to some polls, has nudged ahead recently.

His success was attributed largely to his ability to distance himself from Pinochet. But analysts said the possible return of the former dictator may give Lagos a last-minute boost by reigniting fears that have prevented the right from winning either of the prior presidential races.

Those fears had largely dissipated with Pinochet's absence and Lavin's moderate political stance and youthful, modern campaign.

"But Pinochet's potential return changes everything," said Marta Lagos, who is not related to the candidate. "If Pinochet were returned before Sunday, I'd say it would have helped Lagos far more. But even with it now looking like [Pinochet] may return sometime very soon after the elections, I still think it gives Lagos a new edge by reminding people who Lavin used to represent--and who he still may represent."

Both candidates have said the independent justice system in Chile, which has begun indicting and arresting Pinochet's retired lieutenants during his absence, should be permitted to proceed, and possibly to put Pinochet on trial. But Lavin, who maintains at least one of Pinochet's former ministers in a key campaign position, has tempered his posture by saying human rights and other political issues should be put on the periphery of the national agenda.

Lavin, an economist with a degree from the University of Chicago and a former economic adviser to Pinochet, has in any case sought to play down the issue. "We have to be cautious because this is not for certain yet," he told reporters today.

"No one seriously believes that Lavin is going to focus on human rights issues," said Ricardo Israel, director of the Center for Political Studies at the University of Chile. "Lavin's base of political and financial support is made up of people who were tied to Pinochet during the dictatorship. There is simply no way he can ultimately turn against Pinochet, and Chileans mostly know that to be true."

That is working both for and against Lavin. Many in Chile believe that this nation of 12 million simply does not want to relive--through a Pinochet trial--the horrors committed under his dictatorship, when more than 3,000 people disappeared or were murdered and hundreds more were tortured. And Lagos, although he purposely has not made human rights his primary issue, has zeroed in on the need for justice more than Lavin has.

"I think the sad truth is that most Chileans just want to forget what happened," said Mireya Garcia, a board member of the Associate of Families of the Disappeared. "Now that Pinochet is an issue in the elections, it's very possible people will decide that it's even more reason to vote for Lavin, because they don't want Lagos to rock the boat and start digging up the past."

Lagos, meanwhile, is also trying to play down his support of the ruling coalition's efforts to have Pinochet returned to Chile rather than tried abroad. Lagos, an economist with a degree from Duke University, desperately needs the Communists--3 to 4 percent of the vote--and they could hold that stand against him.

Fueled by the Christian Democrats, Lagos's partners in the coalition, the Chilean government fought hard to have Pinochet freed on humanitarian grounds. It argued that Pinochet should stand trial in Chile rather than in Spain, where a magistrate was seeking his extradition for a trial on his regime's atrocities.

CAPTION: RICARDO LAGOS . . . center-left candidate

CAPTION: JOAQUIN LAVIN . . . right-wing candidate