Tens of thousands of demonstrators marched through Mexico City against the presidential election win of Enrique Pena Nieto, accusing him and his party of widespread vote-buying.
The marchers claim Pena Nieto, from the Institutional Revolutionary Party (PRI), "bought" his way to victory by handing out gift cards and securing paid favorable media coverage from the country's two main TV networks.
"Get out Pena, Mexico without the PRI!" the protesters chanted as the massive crowd made its way down the Paseo de la Reforma -- a main thoroughfare in the capital -- to the Zocalo, the city's giant downtown square.
Mexico's independent election authority on Friday ratified Pena Nieto's victory in the July 1 vote, saying he bested his nearest opponent, leftist Andres Manuel Lopez Obrador, by nearly seven percentage points.
But many in this country of 112 million have refused to accept Pena Nieto's victory, which marks the return to power of the PRI, the party that ruled Mexico for seven decades until 2000, amid accusations of rigged elections and repression.
"We would look really bad if Pena Nieto would take office and we did nothing," said Mara Soto, a 21 year-old student at the National Autonomous University of Mexico (UNAM).
Lopez Obrador, from the Party of the Democratic Revolution (PRD), also came in second in the 2006 presidential election, that time by the slimmest of margins -- less than one percentage point.
He led protests that virtually paralyzed Mexico City for more than a month, claiming fraud in the contest in which outgoing President Felipe Calderon was elected.
Lopez Obrador however has said he was not behind Saturday's march, which participants said was organized online via Facebook, Twitter and activist blogs. Students of the #YoSoy133 protest movement also said they did not organize the demonstration.
Pena Nieto, 45, is set to take office in December. He inherits a country engaged in a brutal drug war and an economy struggling to create jobs. Nearly half of all Mexicans are poor, according to government figures.
Most of the marchers on Saturday appeared to be in their 20s, but families with young children and plenty of middle-aged protesters also attended.
"I'm not young, but I'm with you!" cried out Noe Santillan Ortiz, 50, who addressed the crowd from the base of the Angel of Independence monument, where the march began.
He then screamed himself hoarse leading expletive-laden anti-PRI chants. The crowd followed and roared with approval.
Much of the anger was directed at Televisa, the largest media conglomerate in the Spanish-speaking world, and the smaller TV Azteca.
According to a March survey by Defoe consultants, 90 percent of Mexicans get their news from TV -- which, outside of cable TV, the two networks dominate.
Pena Nieto's wife, Angelica Rivera, was a Televisa soap opera diva and star of telenovelas that include the 2007 hit "Distilling Love."
Critics point to documents leaked to local and foreign media alleging that Pena Nieto paid Televisa for years of glowing coverage. Both Pena Nieto and Televisa deny the charges.
Plenty of anger was also directed at Soriana, Mexico's giant supermarket chain.
Pena Nieto "took advantage of the need of poor people to buy votes," said Gabriel Mendoza, a 54 year-old carpenter, pointing to a yellow Soriana gift card allegedly handed out by the PRI. The card had the logo of a pro-PRI union.
Immediately after the vote, Soriana supermarkets were swamped with people armed with yellow gift cards they said came from the PRI, fearful that the cards would be canceled after the election.
The PRI insists it ran a clean election, and Soriana said the cards with union logos are part of a special buyer's program. At least one PRI governor said the cards were part of a state program to help school children.
On Saturday Lopez Obrador -- who said he will contest the results legally and peacefully -- urged authorities to investigate the vote buying charges, and called on Calderon's conservative National Action Party (PAN) to join efforts to prove that the PRI broke campaign spending limits.
Octavio Aguilar, a senior campaign official for failed PAN presidential candidate Josefina Vazquez Mota, told AFP Friday that he estimates that the PRI spent up to $500 million on the campaign, far beyond the legal limit of $30 million.
"This isn't going to stay like this," threatened Humberto Sanchez, 19. "There will be more marches."