It is a hot sunny day in Chalco, one of the many impoverished areas comprising the misery belt of Mexico City’s south-east flank, and some children are flying a homemade kite on the banks of the Company River, a large and pestilent open sewer whose stench fills the air for many blocks around.
In Aztec times Chalco, a part of Mexico state, which surrounds the capital city, used to form part of a magnificent lake fringed by forested hills. Today it is a sprawling mess of dusty grey streets, poorly constructed housing, bad or non-existent services and failing infrastructure.
But it is also the heartland of Andrés Manuel López Obrador, the leftwing candidate in Mexico’s presidential election, and if he wins Sunday’s vote it will be in large part thanks to the millions of poor Mexicans who live there.
“Without the support base from the capital and Mexico state, López Obrador would be a distant contender in the these elections,” says Ricardo de la Peña, executive president of GEA-ISA, the Mexico City polling company.
According to Dan Lund, a political analyst at MUND Americas in Mexico City, Mr López Obrador dominates the state’s presidential vote – 41 per cent compared with 31 for Roberto Madrazo, candidate for the Institutional Revolutionary party (PRI), and 26 for Felipe Calderón of the National Action party (PAN).
Yet Mexico state is also a bastion of the PRI, which ruled the country for 71 years until 2000. In many of Mexico’s 32 states, the PRI’s once well-oiled machinery has begun to show fatigue. But in Mexico state, which has the greatest number of voters – about 9m, or 13 per cent of the national total – it is still working efficiently.
In the 2003 legislative election, for example, the PRI won 17 districts compared with 13 for the PAN and just six for Mr López Obrador’s Democratic Revolution party (PRD). Only last year it helped deliver a convincing victory for Enrique Peña Nieto, the young and charismatic governor.
Much of the party’s support comes from people such as Fili Salazar, a short and stocky 25-year-old street vendor from Chalco who works in a busy bus station in central Mexico City.
While he sets up a tarpaulin to cover an array of cigarettes, chewing gum and Coca-Cola, he explains that he will vote for the PRI on Sunday mainly out of tradition. “My father voted for them and my grandfather voted for them so I am going to as well.”
So why has Mr López Obrador’s support grown so quickly? According to Ricardo Monreal, Mr López Obrador’s local campaign organiser, one reason is the proximity to the capital, where the 52-year-old candidate was mayor until last year.
Mr López Obrador’s pension for the elderly living in Mexico City, and grants for single mothers and the handicapped, won support not only among millions of poor Mexicans in the city but also among those living close by.
“In some cases the border between the city and the state is a single street so people could actually see how their neighbours were suddenly getting pensions and they were not,” says Mr Monreal. “Those people also want benefits, they know we are doing a good job and that is why they support us today.”
A second reason Mr López Obrador has become so popular has to do with the state’s rapid growth and, in particular, the often unbearable pressure that has placed on the provision of services.
In 35 years the population has quadrupled to 14m – roughly double that of Switzerland – and about 200,000 people move there every year. “In many areas the population is growing so fast that infrastructure cannot keep up,” admits Mr Peña Nieto, the PRI governor.
Reinaldo Ramírez, owner of the forlorn La Michoacana ice-cream parlour just a few yards from the pestilent Company River, moved to Chalco with his family 22 years ago. He does not say who he will give his vote to on Sunday but he is not happy with things as they are.
The smell from the river no longer bothers him – he got used to it a long time ago. But he complains that his humble one-storey home is usually without water, forcing his family to bathe from a small plastic bucket. “It only comes two or three times a week and you can’t drink it,” he says, opening a dry tap to prove the point.
Mr Lund believes it is precisely people such as Mr Ramírez who could vote for Mr López Obrador on Sunday. In many cases, he argues, his votes will even come from people who still plan to vote for their traditional party in the congressional election.
If this so-called “split vote” is widespread, life in Congress could prove harder for Mr López Obrador should he emerge triumphant on Sunday night.
But after a national campaign lasting almost six months, 140,000km of road travel and 681 political rallies, the chances are he will consider that a small price to pay.