Mexican Presidential Rivals Both Claim Win in Tight Vote

López Obrador, wearing a leather jacket with an upturned collar, flashed his signature thumbs-up sign after casting his ballot in his southern Mexico City neighborhood of Copilco. Calderón voted in the upscale Las Aguilas neighborhood with his wife, Margarita Zavala, who is a Mexican senator.

This presidential contest had been the most competitive in modern Mexican history, the first true three-way race in a nation long shackled by one-party rule under the PRI, which was ousted from the presidency by Fox in 2000. Unprecedented numbers of undecided voters, as well as a growing middle class and the permanent class of desperately poor voters, made the outcome difficult to predict in the campaign's final days.

Election officials projected a 60 percent turnout -- more than 40 million of Mexico's 72 million registered voters -- a greater percentage than in typical U.S. presidential elections. Mexico's electoral system has a reputation as one of the world's finest because it employs sophisticated fingerprint and, in some regions, face-recognition techniques to prevent fraud. Still, two recent independent studies suggested that vote-buying and coercion remain problems, particularly in rural areas.

Voting appeared to have gone smoothly in much of the country, though parts of a major Mexico City street -- Avenida Revolucion -- were closed because of protests over a shortage of ballots in some precincts.

López Obrador, who resigned as the capital's mayor in 2005 to run for president, dominated the early opinion polls. His supporters cast him as unstoppable.

But his sheen of invincibility evaporated beneath a withering attack campaign comparing him to Venezuela's Chávez, who has been widely criticized for authoritarian practices and is unpopular in Mexico. López Obrador was slow to respond, an approach his advisers now call a mistake, and Calderón pulled ahead in the opinion polls.

But López Obrador also went negative. In early June, during his only debate appearance, he accused Calderón of helping his brother-in-law get a massive government software contract while Calderón was energy secretary. Calderón vigorously denied the charge, but it seemed to strike a chord with many Mexican voters accustomed to government cronyism, and López Obrador rose in the polls to tie or slightly lead his main rival.

López Obrador, if elected, would have some symbolic hurdles to overcome in his relations with the United States. He would be the first Mexican president in decades who does not speak English and, although he is vague about his travels, it appears he has been to the United States no more than once or twice.

"My sense is that the fact Carlos Salinas de Gortari, Ernesto Zedillo and Vicente Fox were able to communicate in proper English with their counterparts in the U.S. made things easier," Montaño said. "But Lula doesn't speak English, and he's handled his relationship with the U.S. very well," he added in a reference to Brazilian President Luiz Inácio Lula da Silva.

The Calderón-López Obrador showdown was just one of more than 1,000 electoral contests decided Sunday. No single party was expected to win a majority in the legislature, meaning that the next Mexican president will face a daunting challenge in winning approval for his proposals, as well as a formidable check on his power.