After years of exile and scorn for the ballot box, El Salvador's leftist political parties allied with Marxist-led guerrillas are preparing to compete in next year's presidential election.

"Elections here between 1982 and now have been part of a plan designed principally to counter action of the guerrilla army, part of a counterinsurgency project," said Hector Oqueli, organization secretary of the National Revolutionary Movement."It could therefore be argued that we are now lending our support for that same project and that we're contradicting ourselves," he said.

However, Oqueli added, more "political space has opened up" since the presidents of El Salvador and four other Central American countries signed a peace plan Aug. 7, 1987.

"We want to take maximum advantage of that political opening, even though we are certain that doing political work in those spaces is like swimming in a river full of crocodiles," he said in an interview in his party's San Salvador headquarters.

The regional plan has not ended guerrilla conflicts in El Salvador, Nicaragua and Guatemala, but it has contributed to broadening the range of political expression in El Salvador and Nicaragua.

The National Revolutionary Movement, as part of the Democratic Revolutionary Front, has been allied since 1981 with the Farabundo Marti National Liberation Front, the guerrilla organization known as the FMLN that has been fighting the U.S.-backed Salvadoran government for eight years.

Leaders of the political front who had left in the early 1980s because of rampant rightist death squads began returning to El Salvador in November and are still coming.

Among them are Guillermo Ungo, Oqueli and Ruben Zamora, general secretary of the Popular Social Christian Movement.

Zamora's party is a left-leaning offshoot of the centrist Christian Democratic Party of President Jose Napoleon Duarte, who sat on military-civilian juntas in 1980-82 and has governed since 1984. Duarte has cancer and his doctors say it is terminal.

The Oqueli's Revolutionary Movement, the Social Christians and the Social Democratic Party have formed the Democratic Convergence. Oqueli's group announced in July its participation, via the Convergence, in the presidential election set for March. Although the electoral front has yet to announce its participation officially, it is already hard at work launching a campaign.

Zamora, in an interview, said the Convergence's activity "is generating a political alternative capable of attracting ample sectors of the population that have been left without alternative."

"We're also contributing little by little to overcoming people's fear, because of past repression, of participating in politics," he said.

The leftists do not harbor illusions of an electoral victory.

"We are not taking part strictly for the votes, rather we're mounting a historical project that transcends election day," said Oqueli.

The main plank in the leftist platform is a negotiated end to the war. The government has rejected two such proposals by the insurgents so far this year.

"The country's principal problem is the war," Oqueli said. "If the armed conflict is not resolved, we will not be able to resolve the economic, social and political problems - health, housing, nutrition, employment. So we're telling the Salvadoran people that a solution to the war is necessary, and for us that solution is a negotiated political one."

Duarte's position is that the guerrillas lay down their arms before talks can begin, but the rebels say that would be tantamount to surrender.

The guerrillas imposed a nationwide transport ban during legislative and municipal elections in March to underscore their characterization of them as "a farce." The prospect of watching their political allies take part in similar elections next year is thought to be a difficult pill for them to swallow.