Murder raises the spectre of Zapata in Mexico: Assassinated presidential candidate may have taken country's 65-year-old Soviet-style political system to the grave with him

THE mourners seemed to be unaware of the potential symbolism. Beneath the huge letters PRI and slogan of the party that has ruled uninterrupted for 65 years, lay a silver coffin.

Draped in the Mexican flag, the coffin was that of Luis Donaldo Colosio, presidential candidate of the Institutional Revolutionary Party (PRI), whose brains were blown out by a young gunman during a campaign rally on Wednesday in the border town of Tijuana. But was it only the 44-year-old Colosio who was buried on Friday, or did he take with him to the grave the party's long monopoly on power?

Last November, a jubilant Colosio acknowledged the cheers of his militants at the party's Mexico City headquarters. He had just been 'unveiled' by President Carlos Salinas de Gortari as the candidate for presidential elections planned for 21 August.

On Thursday, 116 days later, he was back in the same auditorium, inside the silver coffin, beneath the giant PRI logo, his name still fluttering on 30ft banners on the walls outside. This time, party officials and militants stood in silence before his coffin, stunned by the first such assassination since 1928.

The auditorium was named after General Plutarco Elias Calles, who became president after the assassination of candidate and fellow general Alvaro Obregon that year. General Obregon had driven the bandit- revolutionary Francisco 'Pancho' Villa from Mexico City in 1915, after Villa's brief reign. Many Mexicans of the time suspected that Calles had been behind the killing of Obregon, carried out by a newspaper cartoonist and fanatical Spanish Catholic, Jose de Leon Toral.

Calles went on to found in 1929 what is now the PRI. With an infrastructure comparable with that of the former Soviet Communist Party, the PRI has won the presidency every six years since.

The assassination of Colosio, the favourite to lead Mexico into the 21st century, caused consternation, because not only he but also the PRI and its entire system had been assailed. Mexican newspapers were filled with hundreds of condolence messages, and state television compared the murder with those of John F Kennedy and Martin Luther King.

Colosio's death, and the threat to the PRI, raised the spectre of civil unrest, even revolution or a coup, less than three months after Indian peasants rose in arms in the south-eastern state of Chiapas. Tijuana, where Colosio was killed, is at Mexico's other geographical extreme, but that did not stop some from blaming Zapatista sympathisers for the killing.

Conspiracy theories abounded. The only one that has been all but ruled out was that the confessed killer, Mario Aburto Martinez, 23, was insane.

One of Colosio's bodyguards described him as 'a professional', citing the speed and accuracy with which he killed the candidate at point-blank range. Mexicans were left wondering who were the 'intellectual authors' of the killing.

Pressed by reporters, the Papal Nuncio, Girolamo Prigione, denied any Church involvement in the murder. But after the wake for Colosio, two former presidents, Miguel de la Madrid and Luis Echeverria, hinted that the Church had become too involved in politics.

Many Mexicans believe that the latest turmoil began not on New Year's Day with the Chiapas uprising, but last year when the Archbishop of Guadalajara was shot dead at that city's airport. The official version was that he had been mistaken for a drug baron, but few Mexicans are swallowing that theory: few drug barons use clerical garb. After Wednesday's shooting, television crews and photographers were allowed into a maximum security prison near here to take pictures of Aburto Martinez locked in a glass box reminiscent of Hannibal Lecter's cage. He stared unblinking through the bullet-proof glass at the cameras.

Under the Constitution, which says candidates cannot hold public office six months before an election, the PRI's hands are tied in finding a successor. But Congress was due to meet in emergency session over the weekend, perhaps to alter that part of the Constitution.

The ghost of the revolutionary hero, Emiliano Zapata, whose name was adopted by the Chiapas rebels, appeared to hover over the country after Colosio's death. Zapata's name, too, was on the Mexican Air Force plane that brought the coffin from Tijuana to Mexico City, then on to Colosio's native state of Sonora for burial.

The authorities fear that the latest instability could erupt into violence on 10 April, the 75th anniversary of Zapata's murder. More than 70 civilian peasant groupings said on on Friday that they would support the Zapatista guerrillas, who have not yet accepted concessions offered by the government, and are still said to be calling for Mr Salinas to resign.

The Mexican stock exchange and the peso plunged when markets reopened on Friday, and US border exchange houses were almost double the official rate.

Colosio's wife, Diana Laura, gave an emotional speech before her husband was buried in his home town of Magdalena de Kino. 'He wanted change for Mexico, without violence,' she said. 'He wanted every corner of this country to have a better standard of living.'

(Photographs omitted)