Just after dawn this morning, Enzo A. Doldan arrived at his headquarters here in a dirty, pocked building downtown. He positioned himself behind a bare wooden desk, flanked by his portrait and the Paraguayan flag, and awaited what he calls "my sacrifice for the future."

This is the day of Paraguay's national elections, and Enzo Doldan is an officially sanctioned candidate for president against Gen. Alfredo Stroessner, the most entrenched dictator in the western world.

It has not been an easy task. When Stroessner seized power in this poor, landlocked South American country in 1954, Doldan was an ambitious 38-year-old liberal with a taste for conspiracy and flowery, bombastic rhetoric. Now he is a beefy, 66-year-old outcast with a flushed face and deep bags under his eyes, scorned by both Stroessner and his more militant opposition.

And yet, Doldan has preserved a bit of the old fire. "I have absolutely no doubt," he roared to a visiting journalist, "that we will lose this election by an overwhelming margin."

In the strange, closed world of Stroessner's Paraguay, that declaration might be read as openly defiant. For this country's elections are less a political event than a carefully directed and universally enforced piece of theater, meant to convince both the world and Paraguayans that this is a thoroughly democratic country.

In fact Paraguay, shaped by dictators and devastating wars with neighboring Bolivia, Brazil and Argentina, has had only six contested presidential elections in its 170-year history. Five of them have been held by Stroessner. Every five years, the general suspends a 35-year-old state of siege for a single day, and Paraguay's 1 million eligible voters are required to go to the polls.

When the election stations shut down in a baking late afternoon heat, loyal chiefs of Stroessner's Colorado Party take the ballot boxes away and stuff them with overwhelming and ever ascending majorities for the 70-year-old leader. That the final totals are fraudulent is almost universally accepted by diplomats, Paraguayan journalists and other independent analysts here.

The prized information in the days before an election is not whether or how Stroessner will win, but what percentage has been predetermined. In 1967, in elections for a constitutional convention, it was 68.7 percent; in 1973 it was 84 percent; in 1975 municipal elections, 87 percent; and in the 1978 election, it reached 89.6 percent.

Tonight the Colorado Party announced that it had won the elections with 90 percent of the vote, a slight rise over Stroessner's last win. Doldan captured 5.7 percent.

"In the United States, politics has gotten so advanced with computers that you can know the results of an election two hours after the polls close," said one local journalist, repeating a popular saying here. "But we are still ahead in Paraguay--we know the results two hour before the polls open."

In such an election, the rewards of candidacy are often negatively defined. In August 1964, Doldan and his sons were severely beaten by members of Stroessner's security forces. Now, they have escaped the strong-arm repression because, Doldan concedes, "We have entered into their political process."

"It is worthwhile to be in the elections so that people will learn how to vote, and learn the difference between a bad election and a good election," Doldan added mournfully. "Here they can see the system, see if the votes are counted fraudulently and ballot boxes stuffed. They can see the dead vote."

For Stroessner's more serious political opposition, the answer to an election is in a call for abstentions or blank votes and a show of counter- theater. Hours after the polls opened this morning, eight exiled government opponents flew in on a plane from Argentina in a third "return" organized by major opposition parties, which are excluded from the election.

As in the first two such demonstrations in March 1981 and last September, the exiles were quickly turned around and sent back to Argentina, while their supporters were banned from entering the airport.

"We know perfectly well we're not going to be able to do anything," said Carmen de Lara Castro, the leader of the Paraguay Human Rights Commission and an activist in the major opposition party, the Authentic Radical Liberal Party (PRLA).

"It's all a performance. Paraguay would make a wonderful comic opera if what happened weren't so serious."

The election campaign preceding this year's vote was such that even Stroessner's fiercest opponents tend to describe it with a gentle, chuckling irony.

The two officially sanctioned opposition candidates, Doldan and a close government collaborator, Fulvio Hugo Celauro, were permitted only three rallies and 15 minutes a week of radio time, all of it outside of Asuncion, the only major city in this country of 3 million. They were not allowed to directly criticize Stroessner, and Doldan, the major candidate, had only $55,000 in his yearly party budget.

Against this, Stroessner's monolithic Colorado Party drew on a party budget of about $3 million to "provide what our candidate deserves, in accordance with his personality," according to campaign chief Pedro Hugo Pena, who was interviewed by the newspaper ABC Color. "We fulfilled our slogan that the people be content and the candidate satisfied," Pena said.

Party rallies, culminating in a mass gathering Wednesday night in front of the presidential palace, were filled with farmers and government workers who received memos ordering them to assemble "without exception" at the proper places and times. Both Stroessner's stump speeches and exact crowd counts were then delivered to newspapers and government-controlled media, in at least one case before the rally began.

All the while, Stroessner and his Cabinet chiefs delivered warm, if sometimes peculiar, tributes to the democratic system. "Our political opening came many years ago when the anarchy ended," Stroessner said today as he voted. "We are not deficient in democracy and the people know it. There is democracy, order, freedom, progress and well-being here."

In fact, if Stroessner's government approaches any international political model, it is that of Franco's Spain or Hitler's Germany. The state, Army and Colorado Party form one integrated apparatus that controls almost all political, professional and business activity in the country, and responds directly and only to Stroessner.

All government employes here are required to belong to the Colorado Party, and prospective military officers can be expected to have Colorado parents and Colorado grandparents. Those who resist the system are excluded from profitable careers, and those who oppose it are systematically repressed.

A vast system of corruption greases the chain of command. Paraguay's biggest industry, comprising more than half of its foreign trade, is smuggling. Airports and chunks of the porous borders with Brazil and Argentina are portioned out like small fiefdoms to leading generals, political sources and diplomats say.

By now the political imprint of Stroessner, the last of Latin America's old-style dictatorial strongmen, is so firmly established that diplomats and foreign scholars frequently discount any prospect of real democracy even after his death.

But more optimistic political leaders here point out that as the general has grown old, his country has rapidly changed. Blessed by its partnership with Brazil in the construction of the massive Itaipu dam, the largest hydroelectric project in the world, Paraguay has grown faster than any other Latin American nation in the last seven years. As the new wealth had trickled down, a poor, Indian-based population has gradually grown more independent, these leaders say.

"This is an anachronism, a one-man system," said Miguel Abdon Sanguier, the secretary general of the opposition PRLA party. "It has become a dead end, and when the top man passes it can unravel very quickly. Nicaragua avoided it for 40 years, but it happens sooner or later."

And so even with the rigid predictability of the elections, Paraguayans feel the undercurrent of an unpredictable future.

"We can only look to the future and pray that blood doesn't run here," said Doldan, "that we don't become the next El Salvador."