The success of President Jose Napoleon Duarte's effort to establish viable civilian rule in El Salvador rests, ironically, with one institution - the Salvadorean armed forces, many diplomats and others here say.
If President Duarte can prosecute military officers who have been involved in flagrant human-rights violations, as he has promised, and subordinate the high command to his office, he will break five decades of frequent military abuse of power and open possibilities for full-fledged democracy, these observers say.
Most analysts say the President's record looks good so far, that he has asserted his political power while keeping his ultra-rightist enemies in the military at bay.
But the President's most challenging days are ahead.
The military, still the key power broker, has warmed up to the President because of his uncompromising public support for the armed forces. It and a wide array of civilians support him because of what they believe he will do, not because of what he has done.
Many analysts expect there will come a point when Duarte will find it difficult to keep the delicate balance between expectations and performance. And then Duarte will need all of his political agility to survive.
But now, for the most part, he receives quiet praise. He has insisted on sitting in on Army high command meetings and has moved to curtail the independence of his Air Force chief, Col. Juan Rafael Bustillo, who is aligned with ultra-right politician Roberto D'Aubuisson.
Duarte has met with rebel leaders and even dragged along his tight-lipped and uneasy defense minister, Col. Carlos Eugenio Vides Casanova, to a dialogue with rebels that was hailed by religious and foreign leaders. He has placated his enemies and maintained his base of support more adeptly than many expected.
''We have faith in Duarte,'' says Cristobal Aleman, leader of a Christian Democratic labor group. ''We believe he will move to end the war and support reforms. We believe he is a man who wants to see justice done.''
A young Army lieutenant on patrol in Morazan Province says: ''Duarte has proved that he's a militarist. He believes in the armed forces. He has defended us, and he will not give power to the guerrillas.''
For the moment the armed forces are reaping benefits from Duarte's government. Duarte has easily obtained United States military aid and repaired this country's tarnished image. He has compromised with military chiefs over changes in command in return for transfer of other ultra-rightist military leaders out of the country.
But negotiating command changes, which was arranged before Duarte actually assumed office, is a far cry from prosecuting officers who have abused their power.
It seems as if all of El Salvador is holding its breath, wondering how long this political acrobat can stay aloft.
''I think Duarte can achieve his goals,'' says Dr. Eduardo Molina, a high-ranking Christian Democrat, ''because the military is not the institution it was five years ago. It now supports the reforms. It has had to professionalize itself to fight a guerrilla war.''
The military, most agree, has undergone a profound change. It has evolved from what many have called a Praetorian Guard for the oligarchy into an army that is increasingly more concerned with military strategy than politics. But its cohesiveness as an institution remains. How Duarte will move on rights abuses by the military is one of this country's most intriguing questions.
''Duarte has time,'' says one top official, ''because the Constituent Assembly has turned the Justice Ministry and Supreme Court over to rightists who have no loyalty to Duarte and no interest in investigations. There can be no serious effort to prosecute officers who have committed atrocities until after the March 1985 elections for deputies. If Duarte wins control of the assembly he will then be obliged by his followers to comply with his promises. At that moment will come the most severe test for President Duarte and El Salvador's democracy.''