HAITI IS once again preparing for elections, and it's an anxious time. The last attempt at national elections, three years ago, ended in bloodshed and chaos when gunmen sprayed some of the polls with bullets, killing dozens of voters while soldiers stood by watching. No one doubts that the gunmen were in the pay of the supporters and allies of the former Duvalier regime. The Duvalier family is now out of power and out of Haiti, but many of the people who benefited from it are still there. They haven't enough power to take over the government, but they have had more than enough to prevent anyone else from governing effectively. The elections scheduled for Dec. 16 are Haiti's chance to rescue itself from anarchy and deepening poverty.

This time, despite much unhappy history, the signs are encouraging. The interim government passed an important test of strength last week when it barred one Roger Lafontant from the ballot. Mr. Lafontant, under the Duvaliers, ran the Ton-tons Macoutes, the regime's terror squad and enforcers. An even more important signal was the success of the voter registration campaign last month. More than 80 percent of the eligible population turned out to register.

It's always easy to ask whether the people of a country such as Haiti, with its low literacy rate and no experience with democracy, really understand what elections mean or care enough to make them work. The registration drive gives an impressive answer. Haitians signed up in much higher proportions than Americans do, and they did it in the face of recent events suggesting that it might be dangerous.

To try to avert election-day violence, a number of international organizations are going to have large numbers of observers at the polls. The United Nations is sending a team, the Organization of American States is sending another, and former president Jimmy Carter, who has taken a deep interest in Haiti, will be there with a third. It's a useful way to convey to the Haitian army that it will be held accountable.

Feelings will probably be running high by the time the election is held. As far as it's possible to guess, the leading candidate seems to be a radical priest who is a major threat to the Duvalierists. But if the polling is peaceful and the count is honest, Haiti's neighbors -- beginning with the United States -- will have a responsibility to respond rapidly. The United States is now putting a trickle of aid into Haiti. But with an elected government in office there, this country would have compelling reasons to offer stronger support to a new and fragile democracy lying only a few hundred miles off the Florida coast.