With the free election Sunday of a populist president, the long-oppressed people of Haiti, this hemisphere's poorest country, have overwhelmingly chosen a leader capable of delivering them into democracy.

But Father Jean-Bertrand Aristide will need to play his local political hand adroitly. If he is successfully to hold back the shadows of Haiti's despotic past, he will also require urgent public support from President Bush and Congress.

For 186 years Haiti has waited in vain, through monarchies, desperate presidencies, a failed American occupation and decades of dictatorship for a leader who believed in his country and its people. Since early 1986, when protesting crowds ousted dictator Jean-Claude (Baby Doc) Duvalier, Haiti has floundered, and the United States has dithered as ex-Duvalierists and the corrupt Haitian army successfully used violence to intimidate incipient democrats and to abort elections.

Father Aristide is a breakaway charismatic Catholic priest without government experience. He has not enunciated a specific economic program. People chose him over 10 comparatively bourgeois candidates because of his outspoken and uncompromising opposition to the old ways.

In the election, Father Aristide's weaknesses were his palpable strengths. In the slums of Port-au-Prince, in the middle-class areas of Cap Haitian, in many rural areas of the north and center and even in the distant southwest, Haitians gave hardly any votes to good men with experience and party backing.

Winning is easier than governing. Now Father Aristide will need to forge a successful alliance between his own populism and his mainstream opponents, who are expected to control the legislature. Throughout the campaign too, Father Aristide expressed vigorous anti-American sentiments. Yet he now requires unstinting backing from the United States.

Father Aristide needs to demonstrate publicly his commitment to the country's new constitution, which enshrines a power-sharing relationship between the president and a prime minister elected by the legislature. Previous Haitian presidents have ignored their constitutions and ruled by fiat.

He needs to forsake the rhetoric of revolution for the tougher discourse of renovation. If not, desperately needed investment, both private and public, will stay away. Nor will Congress or the World and Inter-American banks provide the technical and material assistance required.

The youthful new president will need to balance his and his followers' desire for retribution against the death-dealing Duvalierists, especially the Ton Ton Macoutes, or private militia, against Haiti's need for stability.

Haitians have an understandable pent-up demand for destroying the bad guys of their recent past. The army, however, behaved impeccably during the electoral campaign. Without the support of its officer corps, which was counseled by the staff of the U.S. Embassy, there would have been no honest vote on Sunday.

Now there is a basis on which Father Aristide can work with the army leadership. He needs their support for his person as well as for what he represents and what Haitians want. Yet in recent years some in the army have profited from drug dealing, and Father Aristide promised to destroy those who dealt in drugs.

There are real fears that the ex-Macoutes and the army will find Father Aristide too much of a threat and will arrange his assassination. Or the United States could fail to appreciate his full significance as Haiti's hope and could deny him the kinds of backing that would keep his enemies at bay.

Despite his inexperience, Father Aristide now has what no other Haitian leader has ever had -- the undoubted, freely expressed support of the people. With U.S., Caribbean and Latin American backing, he could turn the most deprived country in the Western Hemisphere into a more promising and more stable place.

Moreover, for the future of democracy in this hemisphere, Haiti's ability to produce a meticulously free election should be rewarded.

This election showed what a public and international commitment to democracy could achieve despite enormous logistical and communications obstacles. The role of a determined provisional government was critical. So were the actions of U.S. Ambassador Alvin Adams and his staff. A final ingredient was the presence of nearly l,000 international observers from the United Nations, the Organization of American States and a host of private groups.

Father Aristide not only merits, he cannot succeed without the support of all those who want to give Haiti a chance. The writer, president of Lafayette College, observed Haiti's election as part of a 33-person international team led by former President Jimmy Carter.