It was to have been a classic Argentine Peronist political operation, brokered in advance, sheathed in pageantry, and unveiled to the public as the undeniable formula for a national election.

But only days before its scheduled nomination of candidates for a new democratic government, Argentina's long-dominant populist movement has stumbled. Party conventions planned as showcases of harmony have been paralyzed by factional feuds and court battles. Photogenic embraces have turned to fistfights and even gunplay.

The party's candidacy for president, seemingly fixed by a summit meeting of party leaders, has been cast in doubt. And a widely expected triumphant return to Argentina this weekend by former president Isabel Peron shows no sign of taking place.

Sixty days before an election that the Peronists have been favored to win, the specter of internal anarchy that has haunted them since the death of founder Juan D. Peron seems close to materializing.

"We are giving a bad image to the country. We are running the risk of losing the elections, or electing a government of the worst kind of people," said party leader Raul Matera. "The best people are not going to want to be involved with what is happening."

What is happening has been a troubling spectacle for Argentines expecting democracy after more than seven years of military rule. Following weeks of provincial primary elections, the Peronist party has been holding provincial conventions to select gubernatorial and congressional candidates and delegates to a national convention.

But in the predominant federal capital district and the populous surrounding province of Buenos Aires, party procedures have come unhinged. In bitter factional feuding, local leaders seized control of each convention last week and blocked democratic votes with strong-armed procedures and cadres of raucous--and occasionally armed--followers.

The result has been a week of court battles and tense standoffs between competing sectors that have all but paralyzed the party's reorganization plans. Rival leaders have accused each other of corruption, terrorism, and secret arrangements with the discredited military.

Last night, several Peronist leaders conceded that the party's national convention, scheduled to begin Saturday, may now be postponed as soon as it begins because of the provincial feuding. That would mean that the Peronists, already a month behind the centrist Radical Party in nominating a presidential candidate, could suffer a critical loss of prestige among voters anxious for national stability.

"We are seeing a complete blowup," said one party militant, surrounded by the paper debris of a week of frantic operations in a converted hotel room. "This is the one thing that no one wanted to happen. Everything that was done before was meant to avoid it." The clearest result of the Peronist internal struggle so far appears to be a coalescence of support around the presidential candidacy of Italo Luder, a moderate, low-keyed former Senate president and provisional national president during the last of the Peronists' three previous governments.

But even if Luder's nomination is confirmed, he will take control of a party that appears more than ever to lack a clear identity or defined internal power structure. In the long competition for the presidential candidacy, Luder has appeared to succeed simply by remaining neutral in the complex struggles among factions over leadership and ideology. His plan for government, Peronists concede, so far has been only vaguely expressed.

Moreover, the party's internal conflicts have led many analysts to conclude that the movement has failed to replace the authoritarian role of Juan Peron with stable democratic procedures.

Peron dominated the Peronist movement between l945 and his death in l974. A strong personalist leader with an almost mythical appeal to many Argentines, he served as a final authority over factions in his movement ranging from the extreme right to the exteme left.

Without Peron, factional leaders have repeatedly pledged to reorganize the movement so that leaders and policies are determined democratically. This year, the Peronists successfully organized election primaries in the 23 provinces, and four candidates for president competed for delegates in relatively traditional campaigns.

And yet, the movement's reorganization has been dominated all along by the authoritarian image of Peron and the tradition of factional leaders seeking to broker decisions.

One large party sector, including much of the Peronist-dominated labor leadership, argued that the election ticket should be reviewed--or dictated--by Isabel Peron. For many Peronist leaders, her intervention was seen as the mechanism that would avoid a direct showdown between competing leaders.

But Isabel Peron, who took up exile in Spain after being imprisoned for five years following the 1976 military coup against her, has mysteriously refused to act or even speak in the Peronist reorganization. She has been invited repeatedly to return to Buenos Aires for the national convention, but despite daily reports and speculation over her activities, she has refused even to say whether or not she will return.

With Peron inactive, the party's principal political and labor leaders began working this month to prearrange the choice of national candidates. Because local leaders--comparable to favorite-son candidates in the United States--had won many provincial primaries, no presidential candidate had clearly emerged with majority support.

The Peronist leaders' object was to avoid an open competition for delegates and to convert the party conventions into public displays of unanimity. "If one proposed ticket is going to have 400 of 600 votes," party Vice President Deolindo Bittel was quoted to say earlier this month, "what sense does it make to have 200 people voting against it?"

Last week, the tactic appeared to have worked. In a marathon meeting dubbed "the Peronist summit" by the Argentine press, a handful of top party and labor leaders met with the presidential candidates and determined that Luder would be the choice. His chief rival, Antonio Cafiero, gave up his candidacy and appeared to be endorsed by the leadership for the governorship of Buenos Aires Province.

The trouble started, however, with the provincial conventions. A powerful leader in Buenos Aires Province, Herminio Iglesias, refused to give up his candidacy for governorship to suit the arrangement worked out by national leaders for Cafiero.

Iglesias, a union leader, won the support of some important political and labor leaders, preventing decisive action by the national leadership. When the convention met last Thursday, a "cheering section" of Iglesias' supporters marched into the hall. As they sang and shouted Peronist slogans, the Iglesias-dominated convention leadership rammed through favorable motions by voice votes.

Cafiero's supporters who sought to speak were drowned out or even physically attacked. Finally, Cafiero's delegate bloc walked out as the violence spread. One woman was reported slightly wounded by a gunshot. And Iglesias was proclaimed nominee for governor by those remaining.

After a week of court battles and intensive negotiations, Iglesias' nomination has now been confirmed by the Peronist leadership, preventing a complete breakdown in the party reorganization. But the damage to their movement, Peronists say, has only begun to be calculated.

"The whole country is seeing what happens when its largest political movement tries to organize itself without an authoritarian leader," said a political consultant close to the Peronists. "It's hurting them, and it's hurting the country."