Mexico's traumas deepened at the weekend when the Attorney-General, Antonio Lozano, said last year's assassination of the ruling party's presidential candidate involved at least two gunmen, was the result of a plot, and had been subject to attempts at a cover-up.
The case seemed destined to become "Mexico's JFK" after police detained the alleged second gunman, an activist in the ruling Institutional Revolutionary Party (PRI), who was part of the local security team for the murdered candidate, Luis Donaldo Colosio. Police also arrested the head of the security team and three other bodyguards.
The news will not surprise Mexicans. According to opinion polls, a majority believe Mr Colosio's murder in the northern border city of Tijuana on 23 March 1994 was the result of a power struggle between PRI hardliners and reformers. Mr Colosio was a reformer.
The Attorney-General's report is the first official confirmation that the presidential candidate was not shot by a deranged gunman. But it is likely to undermine further the country's political and economic stability. Foreign investors may question the security of their investments under the PRI government of President Ernesto Zedillo until the identity of the plotters is known.
Mexico's stock exchange, darling of investors until last year, plummeted by more than 15 percent last week as a result of the deadlock with Indian peasant guerrillas in the south and criticism of Mr Zedillo for mortgaging the oil industry as collateral for US financial aid.
Proof of PRI involvement in Mr Colosio's assassination would embarrass the Clinton administration, as the bail-out is intended to bolster Mr Zedillo. While Mr Zedillo insisted he backed the Attorney-General's investigation and blamed the reported cover-up on his predecessor, Carlos Salinas de Gortari, questions are being raised about his conduct before he took office. He had been hand picked by Mr Salinas to replace Mr Colosio as presidential candidate. Although he was Mr Colosio's campaign manager, Mr Zedillo did not attend the Tijuana rally at which Mr Colosio, a popular figure certain to have been voted in as president in last August's elections, was shot.
Mr Zedillo's aides said he did not attend all the rallies and there has been no suggestion his absence was suspicious. Mr Zedillo, a technocrat with no political experience, won the presidency with the lowest vote of the PRI's 65 years in power. His grey image has been battered by the guerrilla uprising in the state of Chiapas, a belief that he must have known Mr Salinas covered up the country's financial plight during the election campaign and his "sell-out" to the US in return for a $20bn (£12m) loan guarantee.
Although the Attorney-General did not say who he thought was behind the assassination, sources in his office said there may have been a conspiracy by PRI hardliners who feared Mr Colosio would threaten their wealth through reforms.
In his report, broadcast on nationwide television, Mr Lozano, a lawyer from the conservative opposition National Action Party (PAN) drafted in by Mr Zedillo to lend credibility to the investigation, implied that Mr Salinas was to blame for covering up the plot.
A special prosecutor appointed by Mr Salinas last year, Miguel Montes, at first said there was evidence of a plot by local security men who, judging by video films, appeared to clear a path for 23-year-old Mario Aburto to shoot Mr Colosio in the right temple. Aburto, grabbed at the scene, has been jailed for 45 years. Mr Montes retracted his theory and opted for the lone gunman view. He was replaced by another prosecutor, Olga de Islas, who also concluded Aburto acted alone.
Mr Lozano said a newly uncovered video "clearly identified" a second gunman, a PRI supporter, Othon Cortes Vasquez, who apparently shot Mr Colosio in the left abdomen while Aburto was shooting him through the right temple. Mr Cortes was arrested on Saturday.