Cover-Up Allegations May Split Ruling Mexico Party : Scandal: Analysts foresee PRI rupture after prosecutor quits, charging interference in murder investigation.

The party that has governed Mexico for 65 years faced potentially its worst crisis Thursday, with analysts and opposition leaders speculating that the Institutional Revolutionary Party could rupture after the dramatic resignation of Mexico’s deputy attorney general and his allegations of a murder cover-up at the highest levels.

In a torrent of political commentary after Deputy Atty. Gen. Mario Ruiz Massieu’s Wednesday resignation, Mexican analysts said the party could split under the weight of the emerging scandal. Ruiz Massieu charged that top party officials had blocked his investigation into the Sept. 28 assassination of his brother, then the party’s second-ranking leader.

Even short of a rupture, most commentators agreed that Ruiz Massieu’s accusations will force President-elect Ernesto Zedillo to choose between the party’s old guard and the progressive factions that Ruiz Massieu appears to represent. Zedillo, a 41-year-old reform-minded economist, will take office next week.

“Ruiz Massieu is sending the president-elect a virtual ultimatum,” Sergio Sarmiento, a prominent political analyst, wrote in a Thursday editorial in the Mexico City newspaper Reforma.

Sarmiento echoed other predictions of a deep party conflict in an interview with Mexico’s English-language daily, the News. “The way Ruiz Massieu announced his resignation creates tremendous pressure within the Institutional Revolutionary Party (or PRI) that could lead to an actual split,” he told the paper.

Much of the speculation focused on the possible emergence of a new party from among ruling-party reformists, probably led by Ruiz Massieu and former Mexico City Mayor Manuel Camacho Solis, who discussed the possibility in a recently published book. Camacho Solis, who most recently served as head of a peace commission formed to negotiate a political settlement with armed guerrillas in the southern state of Chiapas, dropped out of active party politics after a public falling out with Zedillo.

Ruiz Massieu thanked the leaders of Mexico’s two main opposition parties during his emotional resignation speech Wednesday, and later he met with opposition members of the Mexican legislature.

PRI President Ignacio Pichardo and the senator who replaced the party’s murdered secretary general, Maria de los Angeles Moreno, emphatically denied Ruiz Massieu’s allegations. But opposition leaders leaped to defend the deputy attorney general and invite him to future political strategy sessions.

“We agree with the conclusions Mario Ruiz Massieu drew that there no longer is any doubt that this assassination was political from the start and that its motive was political,” declared a statement from the Democratic Revolutionary Party, or PRD, which placed third in August’s national elections.

Leaders of the largest opposition force, the conservative National Action Party, or PAN, called Ruiz Massieu’s denunciations “the strongest blow ever received by the ruling party,” adding hopefully that it could mark the beginning of the party’s destruction.

Party President Carlos Castillo Peraza called a press conference to express PAN’s “admiration” for Ruiz Massieu and his “valor and dignity.” Castillo also called for the resignation of Mexican Atty. Gen. Humberto Benitez, who strenuously denied his deputy’s charges that he too was part of a conspiracy to block the murder investigation.

Responding to calls from the opposition and other supporters of Ruiz Massieu, Zedillo stressed in a press conference after meeting President Clinton in Washington on Wednesday that the probe into the assassination of Francisco Ruiz Massieu will continue until the crime is solved.

Zedillo, who called the deputy prosecutor’s charges “very grave,” made no further comment after he returned to Mexico on Thursday.