Guillermo Manuel Ungo has become the key figure in the political opposition to El Salvador's joint military-civilian junta -- and is thus a top ally of leftist guerrillas bent on winning power.
Once a member of that junta, Mr. Ungo is now its most outspoken single foe as head of the Frente Democratico Revolucionario (FDR), the guerrillas' political arm.
A force in Salvadoran politics for a generation, he led El Salvador's small but vocal Social Democratic Party during the late 1960s and '70s. In late 1979, he was tapped by reformist colonels to become part of the junta they were forming, but he quickly became disenchanted with the prospects of that government and three months later went over into the opposition -- and exile.
Now spending much of his time in Mexico, Mr. Ungo is a quiet, softspoken lawyer. He became head of the FDR 14 months ago, a job that makes him the chief spokesman for Salvadorans opposed to the junta. He works hard at maintaining the unity of opposition groups. He appeals for the support of anyone with a grievance against the ruling junta headed by his former associate, Jose Napoleon Duarte, leader of El Salvador's Christian Democratic Party.
Mr. Ungo, who was born in 1931 to a middle-class family and educated in Roman Catholic schools, has a keen sense of humor and uses it continually. But friends say the humor has become increasingly frayed in recent months as the struggle over El Salvador's future has intensified.
Mr. Ungo is also trying to develop pluralism in the opposition camp. The guerrilla leaders are avowedly Marxist, but many of their civilian allies, like Mr. Ungo, are not. He wants all sides to be represented in whatever government emerges after a guerrilla victory -- a victory he confidently expects.
By his own account, he is close to the commanders of the five guerrilla units in El Salvador -- and has even been called ''the sixth comandante.'' But just how much influence he has is unclear.
Moreover, it is uncertain whether he has a continuing role in Salvadoran politics.
This week, Mr. Ungo is visiting Washington in an effort to build anti-junta support in the United States Congress and press. But he is being ignored by the pro-junta Reagan administration.
The basic unanswered question about Mr. Ungo's future centers on whether the guerrillas, if victorious, would look favorably on him as a part of a new government, much less head it. He may be the most well-known Salvadoran in opposition today, but his role as head of the FDR and his relationship with the guerrillas is tenuous at best.
Asked by reporters in Washington this week whether the guerrillas might simply ignore him if they came to power, he quietly answered with words that suggest he sees a continuing relationship between himself and the guerrillas.
Mr. Ungo and the guerrilla are allies - and they have common cause.
At the moment they jointly oppose the coming election of a constituent assembly. Mr. Ungo says he long supported the electoral process, but that he lacks faith in it now. He was Mr. Duarte's running mate in the 1972 presidential election. By all accounts, they not only won the election, but won it handily. The Army, however, stepped in and, resorting to fraud, declared the result void. Both Mr. Duarte and Mr. Ungo went into exile.
Certainly the junta, headed by Mr. Duarte, has no plan to do business with Mr. Ungo. The two are different in style and approach: The activist Mr. Duarte is more outspoken, the reflective Mr. Ungo quiet. Yet both are committed patriots, democrats, and somewhat opportunistic.
Mr. Duarte as president is trying to do some of the things that Mr. Ungo sought to do during his brief tenure on the junta. Land reform is one of them. Mr. Ungo, however, says the Duarte-sponsored land reform is not working and is simply public relations hype.
Mr. Ungo was allowed back into El Salvador by the military before Mr. Duarte -- and as leader of the Movimiento Nacionalista Revolucionario in the late 1970s was a natural choice for the five-member civilian-military junta that took power in October 1979. That was a short-lived role, however, for he complained the Army was blocking promised reforms.
He and his family fled El Salvador soon afterward -- at about the time Mr. Duarte, having returned, was named to the junta.
Now the two former allies lead opposite sides in the Salvadoran struggle. They have not spoken in months.