Six years ago, Vicente Fox won a historic presidential election here and ushered in a new era of true multiparty politics. Out went the days of rigged elections, hand-picked leaders, and rubber-stamp congresses, and in came a period of more responsive politicians, increasing transparency, vigorous political debate – and vicious negative campaigning.
"[This year's presidential race] has been the most competitive, arguably the most interesting race in our history ... but also the dirtiest," says Julio Madrazo of the CMM consultant group in Mexico City.
The outcome of Sunday's vote will affect whether Mexico will join Latin America's leftward trend or continue to strengthen US ties and focus on free-market reforms.
Andrés Manuel López Obrador, a leftist who portrays himself as a savior of the poor, holds a very slim lead in opinion polls over conservative Felipe Calderón, a proponent of fiscal conservatism and free trade. Running third in polls is Roberto Madrazo, of the Institutional Revolutionary Party (PRI) that governed Mexico from 1929 to 2000. Two other minor candidates have single-digit support each.
But for many Mexicans, notes Mark Schneider, a Latin America expert at the Brussels-based International Crisis Group, it's the negative campaigning, and not the substance that will ultimately drive the vote.
"There is no question that Mexican democracy is maturing with a truly competitive multiparty system," he says. "But unfortunately the political process has not been able to avoid the pitfalls that a media-dominated electoral environment throw up in the way of serious debate over policies and issues."
Latin America's second-most populous country is home to 106 million people and features a wide gap between rich and poor. Local businessman Carlos Slim is the world's third wealthiest tycoon, according to Forbes Magazine – and yet 1 in 5 citizens lives under the poverty line. Mexico is a resource-rich land – but chronic unemployment continues to drive millions every year to sneak across the border into the US in search of work.
On these economic, and other problems, the top candidates offer starkly different approaches.
Mr. Obrador, of the Democratic Revolution Party (PRD), is an opponent of privatization who supports a more active state role in the economy. His plans include creating low-income jobs through large infrastructure projects, and spending more on social programs such as pensions for the elderly. He also says he will review parts of the North American Free Trade Agreement (NAFTA) and refocus attention on domestic policy.
But ask anyone on the street in Mexico City's ritzy Polanco neighborhood what the most important thing about Obrador is, and they will most likely begin talking about Venezuela's populist, anti-American president Hugo Chávez.
"If Obrador wins, we are goners. We might as well move out of the country, because he is a hot-headed vengeful lackey of Chávez and [Cuban President Fidel] Castro," says banker Carlos Molina while picking up a latte at a local Starbucks. "And he is coming after us."
Such fear of an Obrador victory was set in motion by Mr. Calderón's TV ads this March, which repeatedly flashed a clip of the former mayor calling President Fox a "squawking bird." Obrador, intoned a narrator, was "a danger to Mexico." The ads accused Obrador of saddling the capital with huge debts during his five-year stint as Mexico City's mayor, compared him to Chávez, and even insinuated the Venezuelan leader was bankrolling him.
The vitriolic ads were eventually pulled by Mexico's Federal Electoral Institute (IFE) but the message stuck, reinforcing the idea that Obrador was authoritarian, irreverent, out "to get" the wealthy, and would ruin the economy.
Since then, blogs, radio spots, and more TV ads have built on these themes. Mass anonymous e-mails – which are unregulated by IFE – have gone further, warning that Obrador will limit foreign travel and ban religious meetings. One recent e-mail made comparisons between the candidate's fiery populist rhetoric and that of Hitler.
Meanwhile, Calderón, the conservative candidate from Fox's National Action Party (PAN) has also been hurt by negative campaigning. The former energy minister represents pro-foreign investment and pro-business interests, proposes a more active foreign policy, a tighter embrace of NAFTA, and has floated a historic proposal to form a coalition government.
But all anyone can talk about these days is his brother-in-law.
It started at the June 6 debate, when, live in front of 13 million viewers, Obrador accused Calderón with helping channel $230 million in government contracts to his brother-in-law, Diego Zavala, who allegedly evaded taxes on the deals. "Once again, you lie," shot back a surprised Calderón, who has campaigned on a "clean hands" anticorruption platform.
In the days after the debate, Obrador ran multiple TV ads repeating these charges and then, in a widely covered publicity stunt, dumped boxes of what he said were documents to prove the claim at Calderón's campaign headquarters.
Both Calderón and Mr. Zavala have denied the accusations, and even filed a defamation suit against Obrador – but the allegations have resonated, playing off one of Obrador's favorite themes – that the elites in Mexico are prospering at the expense of the poor, and are handing out favors to their friends and family.
In a country obsessed with telenovelas, the campaigns have become a sort of soap opera, says Francisco Abundis, a political scientist and a director at the Parametria polling firm. "Everyone sits tight and sees what one character does, and then holds their breath as they wait to see how the other responds."
And "going negative," says Mr. Abundis, has paid off. "Obrador was winning by 10 points until Calderón started with the negative campaign. It was very forceful and it took about a month to correct this trend, with Obrador only managing to get even by going negative as well," he says.
"The whole negative campaigning concept comes to us directly from the US," says Mr. Madrazo of CMM. "You go to these seminars on how to run campaigns and they are filled with Latin Americans ... and then you come home with DVDs and watch ads of some governor in Oklahoma and figure it out."
Some observers worry that negative campaigning has dangerously divided the country, making violence a possibility if there is no clear winner Sunday. But others, like Gabriel Guerra Castellanos, a political analyst for the daily Reforma newspaper, thinks the mudslinging is actually a sign of a healthy democracy. "We have finally matured into an adult democracy with all its trappings," he says. "We are finally normal.... The campaign has been dirty, which is exactly what happens in other democratic countries."
Mexicans might be obsessed at the moment with Calderón's brother-in-law's finances – but at least they are not focused on election fraud, as has been the case here for decades, says Mr. Guerra. And overall, says the analyst, the intense feelings aroused by the negative campaigning are wonderful. "People are into it. We feel impassioned and we feel we have a stake," he says. "Finally."
• Ms. Harman is Latin America correspondent for the Monitor and USA Today.