Mexico City - It was an intrusion onto sacred ground.
At the height of Catholic Mass in the baroque Metropolitan Cathedral, a man interrupted the service by brandishing a political protest sign at the country's most respected religious figure. Outside, demonstrators chanted, "Norberto Rivera, hell awaits you."
Rivera, a cardinal, oversees the world's largest archdiocese here in Mexico City, the center of religious life in a country where nine in 10 people are Catholic. He had been considered a leading contender to succeed Pope John Paul II after the pontiff's death last year.
But Rivera is now immersed in a nasty political tussle that illuminates the hair-trigger sensitivity here about mixing religion and politics.
On one side, supporters of Andrés Manuel López Obrador, the populist presidential candidate who is challenging the results of the July 2 election, accuse Rivera of siding with the apparent winner, Felipe Calderón. On the other side, Rivera calls protesters who have disrupted Mass at the cathedral "crazies," and other Catholic leaders condemn López Obrador supporters for placing the image of Mexico's most revered saint, the Virgin of Guadalupe, on political posters.
"The mix of religion and politics is always explosive in Mexico," said historian Enrique Krauze, who has dubbed López Obrador a "tropical messiah" because, Krauze says, he tries to use religion to further his political appeal.
Rivera has shown no reluctance to blend the spiritual and the secular, either. Last month, he said the church could mediate the post-electoral crisis.
Two weeks later, he called on Mexican Catholics to respect a decision by a special elections court rejecting López Obrador's request for a full recount and ordering a recount of only 9 percent of polling places. Rivera's statement echoed the position of Calderón, who supported the court's decision, and countered the stance of López Obrador, who lambasted the ruling and continued to demand a full recount. The court is expected to issue a ruling Monday on the electoral challenges.
López Obrador's supporters were outraged by the cardinal's comments. Small groups of demonstrators have stormed into the cathedral during Mass twice in the past month. In the Zocalo, Mexico City's downtown square, where thousands of López Obrador backers have been camping in tents for nearly a month, Rivera's name is uttered derisively.
"He's getting into politics," Alejandro Hernández said, while movie credits scrolled across a television screen in his tent. "The church is for God, not for politics."
Rivera declined to be interviewed. A spokesman, who would not give his name, said, "The cardinal has decided not to give interviews, with the object of not polarizing the situation with his comments."
López Obrador's supporters have interpreted Rivera's remarks as improper intrusions into the political world. Mexican law prohibits religious leaders from direct involvement in politics. But the tension also has roots in history.
Troops supported by the Catholic Church fought a bloody, three-year war against the Mexican government in the 1920s. The war, which cost more than 70,000 lives, was an unsuccessful attempt to overturn reforms that had stripped the church of its considerable influence over the government and the country's financial system.
Even though the church is widely respected and supported -- Mexico has more than 90 million Catholics, more than any country except Brazil -- the war is often cited by Mexicans who want to maintain a strict separation of church and state.
"We fought wars to keep the church out of politics," Hernández said.
Hernández is a churchgoer. But with the doors to the cathedral often closed and guarded to keep out protesters, he now attends services in a tent on the Zocalo.
At the same time, all around him are images that have made Catholic leaders fume. Political posters featuring the Virgin of Guadalupe hang next to signs emblazoned with López Obrador's recount rallying cry: "Vote by vote, polling place by polling place." John Paul II's face shows up on similar posters, as do a bevy of saints. Crucifixes are everywhere.
Mexico's influential Catholic Bishops' Conference condemned the protesters last week, registering its "indignation" about the use of religious symbols and images in the demonstrations. Images of John Paul and the Virgin of Guadalupe had been "adulterated into political symbols," they said.
Critics of López Obrador accuse him of subtly encouraging the use of religious symbols in an attempt to create a messianic following.
"He's playing with fire," Krauze said.
López Obrador generally declines to discuss his religious beliefs, but pictures of saints hang from the tent where he has been living during the protest, and he has not discouraged protesters from using religious symbols.
The demonstrators wrapped in sleeping bags in the Zocalo clearly have no plans to take down their Virgins or their crucifixes. And Rivera seems disinclined to apologize for calling them crazy. So they sit across the street from each other, the protesters and the cardinal, immovable in their grudge match, with church bells clanging overhead.