Peace-broker challenges Salinas: Phil Davison profiles Manuel Camacho, fresh from successful talks with the Zapatista rebels, who is threatening to run for the Mexican presidency

Had they not finally been photographed together, you might have been forgiven for thinking that Manuel Camacho Solis, the Mexican government negotiator, and Sub- Comandante Marcos, the masked Zapatista guerrilla, were actually one and the same person. After all, it is a toss-up as to which of the two emerged as the greater national hero after the brief uprising in the southern state of Chiapas.

Their face-to-masked-face meeting in the old colonial cathedral in San Cristobal de las Casas last month proved that Mr Camacho, 47, could not have been doing a Clark Kent - slipping into a balaclava and honey-coloured contact lenses before emerging from the Lacandon jungle. Nevertheless, so breathtakingly fast was the two men's coincidence of views that it is a theory seriously bandied about among intellectuals in Mexico City that Mr Camacho staged the uprising for his own political ends.

Ridiculous as it no doubt is, the theory gained more proponents at the weekend after Mr Camacho, for long a militant of the ruling Institutional Revolutionary Party (PRI) and close friend of President Carlos Salinas de Gortari, threw down the gauntlet to Mr Salinas and the party that has ruled Mexico for 65 years.

Mr Camacho, devastated last November when Mr Salinas did not name him as the PRI's presidential candidate for elections in August, dropped the strongest of hints that he might cash in on his popularity by running himself if political reforms were not implemented.

'The most suitable path would be that if reforms are approved, my role would be to support democratic transition,' the bespectacled, soft- spoken Mr Camacho said at a news conference in Mexico City. Rumours that he might run for president had already sent jitters through the local stock market and weakened the peso. It was nothing personal, although Mr Camacho is considered more populist than Mr Salinas, but what was at stake was 65 years of tradition.

'Another path,' Mr Camacho went on, 'is that, if there are no democratic advances, if instead of agreement there is polarisation, if anyone seeks to trample on my political rights as a citizen, I would take the necessary political decision to make democracy advance.'

Despite the roundabout language, the message was clear. Either the party changes, or I run for president.

Legally, he could still run for the PRI itself. The party has until one month before the 21 August elections to change its candidate. Or he could run for someone else, perhaps the small Green Party, or maybe work out some kind of alliance with the main opposition Party of the Democratic Revolution (PRD), for which a popular left-winger, Cuauhtemoc Cardenas, has already announced his candidacy.

Whether it be for or against the PRI, Mr Camacho's unprecedented challenge to the system could cause the biggest political earthquake in Mexico since the 1910-17 revolution. The PRI has ruled since 1929 through a system that ensured control of government, legislature, judiciary and labour. Each outgoing PRI president hand-picked his candidate for the next six-year term, a move known officially as 'the unveiling' and on the streets as 'the finger'.

As a lifetime friend of Mr Salinas, a fellow economist, right-hand man in the ministry of budget and planning, former PRI secretary-general and ultimately mayor of Mexico City after Mr Salinas took power in 1988, Mr Camacho considered himself a racing certainty. When Mr Salinas last November 'unveiled' a rival, Luis Donaldo Colosio, as presidential candidate, Mr Camacho, according to a friend, 'turned a whiter shade of pale'.

He quit as mayor in a huff, but in December grudgingly accepted what to many would seem a perfectly acceptable post, that of foreign minister. He had hardly had time to start seeing the world when the Zapatista uprising broke out on 1 January and Mr Salinas appointed him peace negotiator in Chiapas.

Before Mexicans had had time to grasp that the whole thing - armed Indian peasants in balaclavas strolling past unarmed troops into a colonial cathedral, kissing the Mexican flag and calling for the resignation of the president - was not a dream, Mr Camacho had negotiated a ceasefire and a series of accords aimed at improving the lot of the downtrodden indigenous peasants in Chiapas and throughout the country.

Mr Marcos and his fellow Zapatista National Liberation Army (EZLN) negotiators returned to the Lacandon jungle to consider the government concessions.

The only significant demands that were not met were the resignation of President Salinas and a pledge of transition to true democracy. With their friend Mr Camacho in the running, the first could become unnecessary, the second a real possibility.