The people of Guatemala successfully held the first round of their presidential election last week, setting the stage for another Central American version of democratic civilian government replacing military rule.

The vote, with a second round scheduled next month, may have looked to American eyes like the first step toward determining who holds power in a new civilian government for Guatemala. But the men who actually hold power here, and who are likely to continue holding it, were not running for office. They are the generals and colonels who form the army high command.

In a pattern already familiar in Honduras, Panama and El Salvador, now joined by Guatemala, the military is the source of Central American power. Elected civilian presidents are merely those who bargain and maneuver to share some of it. Voter sentiment as expressed at the ballot box has little part in the military's decisions. Instead, officers decide what is good for the military. These conclusions are only sometimes balanced against desires of the elected officials and advice from the U.S. embassy or CIA station.

The struggle faced by Central America's elected presidents is thus to broaden civilian authority as far as possible without exceeding limits set by the military's idea of its own welfare. The struggle of American diplomats in the region is to make that idea coincide with U.S. interests.

At best, this exercise can be noble, swimming upstream dragging the weight of history. The goal -- evolution toward genuine democracy in which elected civilians will hold power along with their presidential sashes -- also seems worth the fight. Its realization would further U.S. interests by eclipsing the Sandinista example in Nicaragua and reducing the danger of more Marxist-allied countries in the region. At the same time, it would give Central Americans -- no less deserving than Americans and Europeans -- the power to determine at the polls who governs them and commands their military establishments.

Viewed from around here, however, the struggle seems to be taking on characteristics of a public-relations exercise, with civilian rule portrayed as a fact in Washington while it is still a hope in Central America.

An event occurred recently in Panama underlining the difference between the appearance and institutions of democratic civilian rule, on one hand, and, on the other, its actual practice in the Central American isthmus.

Nicolas Ardito-Barletta, who lived in Washington and had no political following in Panama, was chosen as a presidential candidate two years ago. According to Ardito- Barletta's recollection later, the choice was relayed in a telephone call from Gen. Manuel Antonio Noriega, commander of the Panamanian Defense Force.

Summoned back from his international banking job, Ardito-Barletta was installed Oct. 11 last year after an election that many Panamanians and some U.S. diplomats said was cooked by Noriega. Secretary of State George Shultz nevertheless attended the inauguration to bless with his presence what was proclaimed the Panamanian democratic process, as if a civilian ruler had been elected in fact as well as form.

Another telephone call from Noriega, this one six weeks ago, dramatically illustrated this had not happened. According to Panamanian and foreign officials with access to the exchange, Noriega ordered Ardito-Barletta to cut short a visit to the United Nations, and report to Panamanian military headquarters. Ardito-Barletta had failed to carry out his assignment to manage the economy. In addition, he had failed to contain a scandal suggesting that Noriega was involved in a death-squad-style slaying of a ominent Panamanian. Therefore, Noriega demanded that Ardito-Barletta hand over his resignation. And Ardito-Barletta complied.

Despite the appearance of civilian democratic rule, the president had no choice. The seat of power remained in the Panamanian military and Noriega was in command. At last report, he still is, despite installation of Eric Arturo Delvalle as the new civilian president. Panamanians, of course, are not told. They have changed Delvalle's nickname from "Tuturo," for Arturo, to "Tuturno," or "Your turn."

The relationship between civilian leaders and military power brokers vary from country to country, of course. The Salvadoran military, for example, has become much more willing to take civilian authority into account than its counterparts in Panama, Honduras and Guatemala.

But only two countries fall completely outside the pattern. One is a U.S. ally often cited as an example of what should happen in Central America. The other is a Cuban and Soviet ally often cited as an example of what the United States is trying to prevent here.

The first, Costa Rica, has for years chosen who runs the government in European-style elections, with the next scheduled early in 1986. The elected civilian president has no need to share power with the military because there has been no army there since 1948, when Jose "Pepe" Figueres disbanded it as a menace to democracy.

In the second, Nicaragua, citizens live under an increasingly Marxist-oriented system that deprives them of many of the liberties their Central American neighbors routinely enjoy. But when the citizens of Nicaragua voted in November last year, they voted on the people and institutions that actually control their government.

This is not to say the Sandinista revolution is an example of democracy or that the Nicaraguan election was an authentic popular verdict. This is to say, however, that no one doubted that if the Front remained in control, Daniel Ortega -- along with his brother Humberto, Tomas Borge and the other six Sandinista commanders -- would actually rule in military as well as civilian affairs. And for better or worse, they have.

Here in Guatemala, the smooth conduct of last Sunday's first round election indicates a runoff scheduled Dec. 8 will come off equally well and a civilian president will take office Jan. 14 after 16 years of direct or indirect military rule. Vinicio Cerezo, a Christian Democrat, is favored to win over his second- round opponent, Jorge Carpio of the National Center Union.

Although Cerezo has favored Guatemalan neutrality in the struggle over Nicaragua, his inauguration still has the virtue for Washington of completing a lineup of Central American nations with Western-style democratic institutions to oppose to Sandinista rule.

But Guatemalans of various political persuasions say that whoever wins the vote will be forced to bargain with the army for the power it is supposed to confer. He will be at a disadvantage, they say, because officers have grown used to power since a CIA-orchestrated coup in 1954 opened a generation of rarely challenged military influence.

In the regional tradition, the new president will have allies in the U.S. embassy. The country desperately needs more U.S. economic aid in the next few years. In addition, the army has set its sights on U.S. military aid, cut off since 1977 over human- rights violations. A $10 million congressional authorization for military aid in 1986 and an increase in economic aid depend on installation of the civilian government and human- rights improvements that must be certified by the embassy.

Aware of this influence, the military chief of state, Gen. Oscar Humberto Mejia Victores, repeatedly has declared that whoever wins will be president. But true to his institution, he also has indicated the army will continue behind the scenes to define the limits of civilian rule. For example, asked at a post-election news conference whether the army would tolerate investigation of past human rights abuses by newly elected civilian officials, he replied: "It would be a mistake if they did that."

His meaning seemed clear -- so clear that Cerezo and Carpio both had already said they have no intention of trying such investigations if elected. In another recognition of the limits of civilian authority, Cerezo predicted that his most critical dealings with the military would be over trying to set human- rights standards for anti-guerrilla operations, seeking control over the army's internal security corps, and monitoring the military budget. If he presses harder than the military tolerates on these matters, he said with a smile in an interview, the outcome could be Guatemala's third coup since 1982.

Honduras, after its own epoch of military rule, had the first in the region's series of elections for civilian presidents four years ago. It has another scheduled later this month to replace Roberto Suaso Cordova. Suaso, a portly country doctor, has made political dealing into local folklore. For example, he not only attempted to pick candidates for the presidential elections for his own Liberal Party, he also tried to choose the candidates of the opposition National Party's. As a result of such wheeling and dealing -- and with strong backing from the U.S. embassy -- he perhaps has acquired more authority than expected.

But the authority wanes when the subject is national security or military affairs, such as the presence of anti-Sandinista rebel bases on Honduran territory. The National Security Council, which makes such decisions in Honduras, has an automatic majority of military officers headed by Gen. Walter Lopez, the armed-forces commander. Their views usually have been determined in advance consultation among fellow officers, if necessary at a meeting of the Superior Armed Forces Council that sets security policy for the country outside the civilian political debate.

The Honduran military prefers to remain in the background, leaving the civilian government out front as if it were in charge. But -- in a telling crisis last spring -- officers had to rein in Suaso's love of political maneuver openly. After a dispute with the legislature boiled into a showdown, Suaso ordered some legislative leaders expelled from the country. Several military officers were ready to comply and got an airplane ready.

According to a source with firsthand knowledge, U.S. diplomats, fearing that the appearance of constitutional rule was about to crack, pleaded with the officers to change their minds. This created the interesting situation of U.S. officials urging Honduran soldiers to disobey their president.

Lopez finally called the whole thing off. By thus setting up an open military intervention to resolve the crisis, he signaled to Suaso that he was orverreaching. The institutions of constitutional rule thus were preserved, but only when the ultimate authority -- the military -- stepped in to lay down that law.

Jose Napoleon Duarte of El Salvador has avoided such embarrassment by being much more cautious, working in close concert with Gen. Carlos Eugenio Vides Casanova and his military high command. By avoiding sticky points such as prosecution of military human-rights abusers, Duarte has been steadily accumulating an appearance of presidential authority since his inauguration 18 months ago.

And there have been some happy changes in El Salvador during this time. There has been a sharp drop in the number of death- squad killings and the near eclipse of Roberto D'Aubisson, the former intelligence major who had been a champion of the no- holds-barred right wing. But this is less a function of Duarte imposing these reforms, and more a recognition on the part of the officer corps that these improvements will redound to the military's interest.

What it amounts to is that the U.S. Congress, by more than doubling military aid, has made the trappings of civilian rule worthwhile for the Salvadoran military.

The momentum has now been slowed, however, by the recent guerrilla kidnaping of Duarte's daughter. By swiftly agreeing to release high-ranking rebel prisoners in exchange for his daughter, according to Salvadoran and U.S. sources, Duarte angered several powerful military officers. In secret contacts later described by military sources, they sought to persuade the high command to forbid the trade.

After a strong statement backing Duarte from the U.S. Embassy, the disgruntled officers failed and the deal received a khaki imprimatur. But the harm had been done. Duarte's obligation to duel with from the high command -- of which he in theory is the commander-in-chief -- already had brought back into the open the military's ultimate authority. The rebel command -- the Farabundo Marti National Liberation Front -- was quick and emphatic in pointing this out, naturally enough. And most Salvadorans had never lost sight of it in any case.

Only to the degree that Duarte's civilian democratic rule actually takes root can it rob the rebel movement of appeal among Salvadorans. The same could be said for Guatemala and for the appeal of any plans for Sandinista-supported rebellions in Honduras or Panama. For the Central Americans who live under behind-the-scenes military rule, particularly with its history of brutality and corruption, the civilian institutions that look good from afar are not enough.

The Reagan administration, however, which has Congress and public opinion to deal with, seems to declare the democratic process in place once a Central American president has been elected and installed. Congress, reluctant to impede the process once it is declared underway, accepts elections and democratic institutions as the measure of democracy in deciing on U.S. aid, without demanding that the institutions actually function with authority over the military.

The region's elected civilians, equally reluctant to endanger the process -- and sometimes their own positions -- have tended to accept the measure of power accorded them by the military. Military officers therefore retain ultimate authority even if they defer exercising it to obtain the U.S. aid money that comes with a democratic process.

This situation probably does not give Central Americans authentic democracy. But it does give them the institutions and appearance of accepting democracy and the hope of attaining more. In addition -- and perhaps more to the point in many eyes -- it clears away obstacles to U.S. aid for pursuit of some of the administration's more concrete and less-heralded regional objectives:

*Defeat of El Salvador's leftist guerrillas.

*Defeat of Guatemala's leftist guerrillas.

*Isolation and denigration of Nicaragua's Sandinista government

*Alignment of Central American nations in a concert of governments supporting U.S. policy against Nicaragua and preventing any Contadora agreement that does not meet U.S. standards.

*Security for the Panama Canal and U.S. bases in Panama.

*Continued use of Honduras as a U.S. staging area and intelligence platform against Nicaragua and a headquarters for U.S.-sponsored Sandinista guerrillas.