Of the many scenes of Haiti that have stayed in my mind since a visit to Port-au-Prince 18 months ago, one has a vividness of its own: the bravery of Gregoire Eugene. He is a journalist and politician who led the opposition to Jean-Claude Duvalier, the ex-dictator and the newest millionaire playboy on the European circuit.

On the Sunday afternoon that I and two others from the Committee to Protect Journalists arrived in Haiti, we went directly to the home of Eugene. He was under house arrest. Months before, Eugene, editor and publisher of the often confiscated newspaper Fraternite, and founder of the Haitian Christian Social Party, had returned to Haiti after four years of forced exile. Eugene lived in a neighborhood that was plush by Haitian standards: paved streets, electricity and running water, a patio here and there.

Minutes after our group arrived, the police appeared. They stood at the locked gate and told us that seeing Eugene was forbidden. Don't try. At this point, Eugene emerged. He spoke to the police, then to us. His bravery was in appearing at all. He risked giving the police another reason for confinement: collaborating with outsiders. Eugene had no civil rights and no civil liberties. Earlier in 1984, his newspaper, car and printing equipment had been seized, following his being jailed overnight and put under house arrest.

With a letter of support that we slipped to him, Eugene left and went inside his home. Last week, with Haiti rid of the 29-year curse that was the dictatorship of Duvalier senior and then junior, Eugene announced that he would seek the country's presidency.

Other qualified candidates are likely to emerge. None will be able to offer Haiti's six million people much more than a promise that the future can't be any worse. No country in the hemisphere is poorer. The lucky few who have jobs start with a minimum of $2.50 a day. The country's largest newspaper has a circulation of less than 10,000. With about 80 percent of the population illiterate, few people have use for a newspaper. Haiti is a nation of thin people. Food is scarce because what little farmland there is has suffered catastrophic soil depletion.

Except for a well-run AID program and sending in Peace Corps volunteers two years ago, the Reagan administration has no record in Haiti to be proud of. This is the administration, with the Coast Guard at sea and the Justice Department with paddy wagons at the docks, that imprisoned boat people. Four years ago, when I visited the Krome Avenue prison -- west of Miami on the edge of a swamp -- Haitians languished while public-interest lawyers sought relief through the courts. Each Haitian that I interviewed expressed fear of death or persecution if he were sent home. The black and poor Haitians suffered a fate rare for immigrants: jailed on arrival in the land of the free.

As is heard now in the government's roundup of Salvadoran refugees, the Haitians had no right to be here: They were fleeing poverty, the State Department said, not persecution. The department's 1983 report on human-rights practices says that none of "those interviewed after their return to Haiti have reported mistreatment as a result of their attempt to emigrate." Americas Watch, the New York-based independent human-rights group, contradicts that. The department's "report does not say that only a small fraction of the total number of people who were returned to Haiti . . . have been interviewed. In some instances, State Department officials have been unable to locate those who are supposed to have returned. U.S. officials continue to refuse to make the names of those who have returned available to private groups interested in investigating the fate of these people."

It isn't a coincidence that the violent revenge now occurring in Haiti is directed at the Ton-Tons Macoutes, the Duvalier security force that killed randomly those it suspected of dissent. The Washington Office on Haiti, a publicly funded human-rights group, says that the Ton-Tons are the logical object of the current revenge: They were killing and beating the Haitians sent back by the Reagan administration.

The State Department, practicing a style of voodoo politics that tried to exorcise the inevitable, backed Duvalier until nearly the end. The dictatorship with one of the worst human-rights records in the world regularly received high ratings for its "concrete and significant" effort of moving toward democracy. Few signs appeared that the United States wanted the downfall of the dictator it had consistently pampered.

Leaders like Gregoire Eugene need to write a constitution, control the military, free the press, end corruption and feed the hungry. Any one of those near-impossibilities will demand the talents of a magician and the vision of a saint. If Eugene and others receive from the United States the kind of positive support that Duvalier enjoyed, a small chance for reform exists. Under Duvalier, there was no chance.