In their eagerness to assure the world that Sunday’s election was free and fair, Mexican President Felipe Calderon and the country’s top electoral officials seem to have glossed over a few dirty details.

The election, it appears, might not have been so squeaky clean after all.

That is the suspicion emerging here, in the days after preliminary vote tallies by Mexico’s Federal Election Institute (IFE) gave Enrique Peña Nieto a six percentage point win over second-place finisher Andres Manuel Lopez Obrador, who represents the country’s left.

The initial count shows Peña Nieto’s margin of victory was more than 3 million votes, an advantage that should be wide enough to overcome any legal challenge to his win, including Lopez Obrador’s demand for a full recount of the ballots.

President Obama and other foreign leaders called Peña Nieto to congratulate him on his victory Sunday night. He has been declared the “virtual president” by the Mexican media and has been busy giving speeches laying out an ambitious agenda. Final results are due by Sunday.

But the whiff of suspicion building over Peña Nieto’s win has less to do with the overall vote tally than the way the presidency was won.

Peña Nieto campaigned on a promise to break with the heavy hand and dirty tricks associated with his Institutional Revolutionary Party (PRI), which ruled Mexico for seven decades until 2000.

PRI activists allegedly handed out prepaid gift cards from the grocery chain Soriana to voters in some districts, according to amateur videos broadcast Wednesday on Mexican television networks and reports in Mexican media.

The alleged card recipients mobbed at least one store on the outskirts of Mexico City in a panic after rumors spread that the cards would be invalidated. According to the Associated Press, each card was worth 100 pesos, about $7.50.

“It was neither a clean nor fair election,” said Eduardo Huchim of the Civic Alliance, a Mexican watchdog group funded by the United Nations Development Program.

This was bribery on a vast scale, said Huchim, a former IFE official. “It was perhaps the biggest operation of vote-buying and coercion in the country’s history.”

But even he acknowledged that the vote-buying and coercion that his group is alleging will not change the election’s outcome.

It’s not against the law in Mexico for political parties to give out gifts — such as school supplies, a sack of cement, a hot lunch, or even prepaid gift cards. And all three major parties of the country do so, in national, state and municipal elections.

The gift expenses must be reported to election officials, and total spending cannot exceed campaign limits. Violations are fined, but well after ballots are cast, and campaigns routinely consider the penalties the cost of getting elected.

However, it is illegal to directly buy votes with gifts.

The Civic Alliance also said that the PRI employed child lookouts as young as 8. The “niños halcones,” or “kiddie hawks,” were allegedly sent to some polling stations to guarantee that voters marked their ballots as they were paid to do.

The watchdog group said members who were sent to observe 170 polling stations reported a dozen instances of children spying on voters.

Peña Nieto said that the election was not stolen and that the PRI did not buy a single vote. His director of international affairs, Emilio Lozoya, said, “These prepaid cards have nothing at all to do with the election.” He also said that the party and campaign denied using children to watch anyone vote.

Lozoya said the cards were purchased by the government of the State of Mexico and given to recipients as part of a social-
welfare program. Other prepaid cards were distributed through the Confederation of Mexican Workers. He said the rumor that the cards were given to people by the PRI in exchange for their votes was being spread by the party of the second-place finisher, Lopez Obrador.

Until now, the president-elect and his party have been more focused on the vote count, and not on the allegations of vote-buying and coercion.

“We are calm because we won the election, and if we recount the votes, we will win again,” Luis Videgaray, a top campaign official for Peña Nieto, said on Mexican radio.

Videgaray said Lopez Obrador and other critics “should stop fighting the arithmetic.”

A recount of more than half of the ballots is underway, and the IFE said it is looking into the fraud allegations.

Mexico’s ruling National Action Party (PAN) has not challenged the results, but the Lopez Obrador campaign said it had detected irregularities at 114,000 of the country’s 143,000 polling stations and was amassing evidence of widespread vote-buying and other forms of cheating.

“This election was a national embarrassment,” Lopez Obrador said.

The leftist also had alleged fraud during the presidential race in 2006, when he lost to Calderon by half a percentage point. His protesters staged demonstrations that carried on for months.

The allegations of vote-buying undermine the narrative pushed by Peña Nieto that he belongs to a new, more honest and transparent generation that has renounced the coercion, threats and dirty tricks of its elders, “the dinosaurs” of the old PRI who delivered the vote and kept people in line.

“If Lopez Obrador can prove that PRI engaged in serious and systematic buying and coercion of the vote, then it would call into question the validity of the results — no matter what the vote count is,” said Eric Olson, associate director of the Mexico Institute at the Woodrow Wilson Center in Washington. Olson was in Mexico City to monitor the election.