Mexicans awaited clearer results Wednesday from a presidential election that Enrique Pena Nieto looked to have won handily before chief opponent Andres Manuel Lopez Obrador cried foul.
Lopez Obrador, who leads a leftist coalition, has demanded a recount and alleged massive fraud, accusing Pena Nieto's center-right Institutional Revolutionary Party of distributing 1.8 million gift cards to buy votes.
Voters in Sunday's presidential and legislative elections are accused of "proving" they voted for the PRI by showing party officials a cell phone picture of their ballot paper before being handed gift cards in return.
Soriana, a major Mexican store chain, printed a full-page ad on Wednesday after their shops were swamped by people rushing to buy products with gift cards they apparently feared might be cancelled soon by the authorities.
It is "absolutely false" that cards with the logo of the Confederation of Mexican Workers, a major pro-PRI union, contained cash, "because those cards only offer discounts and loyalty points," Soriana said.
PRI spokesman Eduardo Sanchez flatly rejected the charges.
"We have not handed out any cards. Neither the Enrique Pena Nieto campaign nor the PRI have any relationship with those cards," he said. "We will not carry out the legal challenge in the media, everything is in the hands of the electoral authorities."
Before the vote, Lopez Obrador's coalition, headed by the Party of the Democratic Revolution (PRD), filed an official complaint with election officials over alleged PRI gift cards to be used at PEMEX gasoline stations. Separately, the ruling conservative National Action Party (PAN) filed a complaint about alleged PRI bank cash cards.
"There is no doubt that there was not a fair and transparent election," Lopez Obrador said Tuesday, accusing Pena Nieto and the PRI of having bought "millions of votes."
The first official results from Sunday's vote showed Lopez Obrador with 31 percent of the vote against 38 percent for Pena Nieto of the PRI.
Observers fear Lopez Obrador's refusal to concede could trigger a repeat of the 2006 presidential election, when he lost by less than one percent, claimed fraud and organized mass protests that paralyzed Mexico City for more than a month.
Lopez Obrador claims that the PRI, through its national party and governors, spent millions of pesos buying votes. He also charged that the news media heavily favored the PRI and that the party shattered campaign spending limits.
The percentage difference in Sunday's vote amounts to some three million votes, election officials say, a wider margin than in the last presidential election but closer than various pre-vote surveys had indicated.
A new round of clearer results were due to be announced later Wednesday, with a final official tally expected by Sunday.
Officials with the Federal Electoral Institute (IFE), which organized the vote, held an emergency meeting Wednesday, as protesters marched outside the office. On Tuesday, they said results from one third of all polling stations could be subject to review.
The PRI was synonymous with the Mexican state as it governed for seven decades until 2000 using a mixture of pervasive patronage, selective repression, rigged elections and widespread bribery.
Pena Nieto, who declared victory late Sunday, inherits a country beset by a brutal drug war, an economy struggling to create jobs, and political turmoil as his chief opponent refuses to concede.
The youthful-looking 45-year-old leader has moved quickly since Sunday's election to try to allay fears that the corrupt practices of the once authoritarian PRI could make a comeback.
"We are a new generation. We are not returning to the past. My government has its sights set on the future. Mexico has changed," he told foreign reporters on Monday.
There is no run-off vote in Mexican presidential elections, meaning that about 62 percent of the electorate did not vote for Pena Nieto.
Marches are likely to follow in the next days and will tap into that anger, but it is unclear how long they will last, or how many people will follow Lopez Obrador.
Leaders around the world, including US President Barack Obama, have already congratulated Pena Nieto on his apparent victory.