Whether the slim win of conservative Felipe Calderón is certified by an electoral court or leftist leader Andrés Manuel López Obrador ends up ahead after his legal challenge runs its course, Mexico's disputed July 2 election has already become a tale of a polarized nation split along regional, class, and, now, party lines.
The two rival presidential candidates split the country's 31 states and one federal district right in half, winning 16 each. Mr. Calderón's National Action Party (PAN) and Mr. Obrador's Democratic Revolutionary Party (PRD) hold nearly opposite views on most issues, and each gained more legislative clout in Congress. Both have throngs of supporters convinced of their candidate's victory.
Such partisanship has stirred fears of legislative gridlock over the next six years, while dealing the long-ruling Institutional Revolutionary Party (PRI) a severe blow. But many analysts say that, in the new political landscape, a weakened PRI could ultimately help Mexico push through the labor, fiscal, and energy reforms that eluded President Vicente Fox.
"[The PRI] is no longer a power broker, but a power seeker," says Federico Estevez, a political science professor at the Autonomous Technological Institute of Mexico. "It makes for a Congress that will actually move legislation."
Because the political story is still unfolding in Mexico, with no president-elect and the PRI recovering from a loss that transformed it from the largest bloc in Congress to the third largest, it is unclear how coalitions will ultimately take shape.
The PRI spent most of the Fox presidency standing in the way of his reforms. Now they realize they need to reinvent themselves, analysts say, by finding middle ground between two parties that offer strikingly different formulas for equality and prosperity in Mexico.
"If the two dominant political parties are not on good terms at the moment ... the PRI could be the best option for putting together consensus," says Lorenzo Lazo, a political analyst in Mexico City who served in several PRI administrations.
Many expect that a Calderón win would attract a market-friendly faction within the PRI. Armand Peschard-Sverdrup, a Mexico expert at the Center for Strategic and International Studies in Washington says this faction is trying to gain control after Roberto Madrazo's third-place finish in the election. "That the more technocratic faction of the [PRI] seems to have been vindicated [by Madrazo's loss] ... presents more favorable conditions than the ones that Fox has encountered since 2000," he says. Such a coalition could improve relations with the US, analysts say, if the Mexican Congress succeeds in making labor laws more flexible or increasing tax collection to boost government coffers, an effort at which Fox failed.
If Obrador emerges as a victor, the more "social democratic" factions of the PRI could defect to his party, says Dan Lund, a pollster in Mexico City.
But it could be weeks before any such scenario is realized. Earlier this week Obrador filed more than 800 pages, as well as photos and videos, to the electoral tribunal alleging that the election was marred by fraud.
Wednesday his supporters from the country's 300 electoral districts headed to Mexico City, where a second mass rally is planned for Sunday.
Calderón cannot be declared president-elect until the electoral court takes up allegations of fraud. The tribunal has until Sept. 6 to certify a winner.
Coalition-building will be a challenge for Mexico's budding democracy, say analysts, pointing to the fact that the political culture here was fostered under 71 years of authoritarian rule under the PRI. "It is really new for Congress to be more than just a rubber stamp," says Laurie Freeman, Mexico associate at the Washington Office on Latin America think tank.
Yet even if the ruling party manages to build coalitions, the public might be more defiant. The industrial north, which has benefited from free-trade agreements like NAFTA, went overwhelmingly for Calderón, while the poorer south has embraced Obrador – which could make it hard for voters to eventually legitimize a winner.
"Fraud! Fraud!" Lopez Obrador supporters screamed through packed streets feeding into Mexico City's public square, the Zocalo, at the first of his rallies last weekend to contest the election. "If there's no solution, there'll be revolution!" they chanted.
Calderón, whom Obrador accuses of acting like the winner prematurely, has pledged to build alliances both across the nation and in his cabinet.
"I offer my hand to my opponents and it will be there until someone replies," he said this week.
But some doubt that coalitions will be easy to form, or that the PRI will emerge as a cohesive block. The internal divisions within the party could prove to be insurmountable, says Andrew Selee, director of the Mexico Institute of the Woodrow Wilson International Center for Scholars in Washington. "The PRI has everything to gain by being a dealmaker," he says, "but there are large sectors [within the PRI] that don't see it that way, who would rather be part of the opposition."
• Ms. Llana is Latin America correspondent for the Monitor and USA Today.