MEXICO CITY — Felipe Calderon grew up as a play-by-the-rules, straight-A student who loved soccer and learned to shake hands and go home when the whistle blew.
His opponent in the presidential campaign loved baseball and settled disputes on a dirt field with fists-flying brawls.
Now with the 2006 election declared over, a defeated Andres Manuel Lopez Obrador is charging off the mound and threatening to draw all of Mexico into the fight.
Using incendiary speeches and force of personality, Lopez Obrador has persuaded more than one-third of the country that Mexico's July 2 presidential contest was manipulated so that Calderon would win.
Lopez Obrador's critics say that along the way, he has inflicted severe damage on Mexico's still-fragile democratic institutions, including the Federal Electoral Tribunal that Tuesday declared Calderon the winner.
To Lopez Obrador, that seems to matter little.
"To hell with the institutions!" he declared in a lateafternoon speech, echoing his new favorite line and vowing to continue what he portrays as his fight for Mexico's poor.
Since the election, Lopez Obrador has rallied supporters to demand a recount of the election, bringing them out into the streets to pitch their protest camp in Mexico City's central square and along its main boulevard. President Vicente Fox and much of Mexico have stood by waiting for the protest movement and its tent city to fold under the weight of summer rains and the scorn of citizens angry over traffic jams and lost business.
But Lopez Obrador sees the declaration of his defeat as one in a long line of corrupt acts by Mexico's elite, aides say. His political history provides little indication that he will back away from the confrontation.
In 1994, Lopez Obrador lost the governor's race in his native state of Tabasco. The protests he staged then lasted more than a year. He dropped the campaign only when he took over as president of the Democratic Revolution Party, or PRD, in 1996.
There appears to be no similar exit this time.
Fox has three months before Calderon is scheduled to take office and, in theory, could use that time to find a graceful solution. But Calderon's advisors and outside analysts agree that Fox has been passive during the summer and has so far shown no sign of taking a more active role.
"There is little Fox can do to keep from leaving a mess for Calderon," said Pamela Starr of Eurasia Group, a risk analysis firm. "I don't see the opposition weakening over the next three months, and the option of trying to crush it will only strengthen it."
Instead, the two sides appear to be maneuvering in ways likely to deepen their confrontation.
On Friday, lawmakers sympathetic to Lopez Obrador on their first day of work took over the congressional dais and blocked Fox from delivering his State of the Nation speech.
Now, Lopez Obrador supporters are signing up to serve as delegates to a national convention that he says will discuss forming a new government. The convention is to meet at a Sept. 16 rally he insists be held in the path of the military's annual Independence Day parade.
In daily speeches to thousands of supporters who have pitched camp, Lopez Obrador has declared he will neither negotiate with a Calderon administration nor recognize its legitimacy.
Members of Calderon's transition team are scrambling to build a congressional coalition with the country's longtime ruling party, the PRI, which came in third in the presidential election and with any members of Lopez Obrador's party they can lure away.
Calderon's team is offering Cabinet positions for the right combination of cooperation and deliverable congressional votes -- the sort of actions that Lopez Obrador could easily view as further proof of political corruption.
The standoff means Calderon's promise of making Mexico into a country millions of citizens will no longer wish to flee is going to be especially tough.
At the same time, however, Lopez Obrador may have succeeded in forcing Calderon to focus attention on the country's social inequalities.
Calderon's advisors say they know they must pass some kind of high-profile legislation to address the misery of the poor if they want to contain Lopez Obrador's popularity.
"The messianic Andres Manuel Lopez Obrador has done a great service to his people," said George Grayson, a political science professor at the College of William & Mary in Virginia and author of a Lopez Obrador biography.
"He has put the fear of God in Mexico's pampered elite, who live well, pay relatively little in taxes, neglect the poor, and spend anemic amounts on healthcare and education for the masses."
In the end, that fear could give Lopez Obrador not the office he seeks, but at least some of the political victories he desires, suggested Armand Peschard-Sverdrup, a Mexico expert with the Center for Strategic and International Studies in Washington.
"The common denominator between the two camps is the acknowledgment that there needs to be a better focus on addressing social inequalities," he said.
"Calderon is aware that a social agenda has to be a pillar of his presidency, not only because the election exposed the two Mexicos, but because of the political pressure Lopez Obrador exerts."