Obrador, who is universally known by his initials AMLO, will succeed Enrique Peña Nieto of the PRI (Institutional Revolutionary Party) who was elected amid high hopes in 2012 but ultimately failed to revive the economy or tackle the widespread corruption and violence linked to the drugs cartels.
AMLO, a silver-haired 64-year-old who has drawn comparisons with Britain's Labour Party leader Jeremy Corbyn, was elected under the slogan of No Les Voy A Fallar (I Will Not Fail) and now has a mandate to carry out widespread reforms of Mexican society.
But one of his campaign promises was to scrap a US$13billion six-runway airport which is being constructed on the outskirts of Mexico City by the billionaire tycoon Carlos Slim.
The airport, expected to be completed in 2020, was first proposed in 2001 by Peña Nieto's uncle, Arturo Montiel, who was governor of Estado de Mexico, a state which includes many of the suburbs of Mexico City.
My warmest congratulations to Sr. Andrés Manuel @lopezobrador_ on his victory in Presidential elections in Mexico. Muchas felicidades! Look forward to working closely to advance India-Mexico Privileged Partnership.— Narendra Modi (@narendramodi) 2 July 2018
Mexico City has a population of nearly nine million but when its suburbs are included around 21 million people live in the metropolis.
44 Million Passengers Use Existing Airport
The city's current airport, Benito Juárez International, is the busiest in Latin America with 44 million passengers a year and only two runways.
Congratulations to Mexico's brand new hope. Amlo's victory proves that there comes a time the mafia-like establishment loses its grip and hope takes root. It is now up to the progressives in Mexico and beyond to seize the day and ensure that the people's verdict is honoured— Yanis Varoufakis (@yanisvaroufakis) 2 July 2018
The original plans for the airport were blocked by opposition by communities living near the proposed runways.
But the idea was revived under Peña Nieto and the state-owned company Aeropuertos y Servicios Auxiliares began preliminary work on its construction.
The land, which was swampy as it was once part of Lake Texcoco, has been drained and pilings have been drilled in an attempt to stop the runways and terminals from sinking.
AMLO's plans to scrap the airport are expected to get the support of the new Mayor of Mexico City (Distrito Federal), Claudia Sheinbaum, a left-wing scientist who believes it will increase the city's chronic air pollution.
But is the airport now a juggernaut that cannot be stopped?
Carlos Slim Backs New Airport
Mexico's richest man, Carlos Slim, certainly hopes so.
Slim made most of his fortune in telecommunications — he owns Latin America's huge Claro network — but he has his fingers in many pies and the new airport is one of them.
His companies have an eight percent share in Mexico City Airport Trust, which raised $6 billion in September 2017 through a bond issue to fund the airport construction.
Congratulations to Mexican President-elect Andrés Manuel López Obrador.— Antonio (@AntonioArellano) 2 July 2018
The Mexican people deserve a bright and vibrant future reflective of our brilliant culture. May this change bring prosperity, and peace to Mexico. #AMLO
In January one of Slim's companies was awarded the contract to build the terminal buildings.
The International Air Transport Association said in April that abandoning the airport project would lead to a US$20 billion reduction in Mexico's gross domestic product and the loss of 200,000 jobs.
Ironically Slim's son-in-law Arturo Elías Ayub was one of 300 Mexican businessmen who endorsed PRI candidate Jose Antonio Meade only last week.
Meade trailed in third place, with a miserable 16 percent, as voters sided with AMLO, who lashed out at big business and vested interests.
Will He, Won't He?
So will AMLO shelve the airport?
In April, Bloomberg reported the value of the bonds had rallied after AMLO promised to protect bond-holders even if he did not go ahead with the project.
AMLO has said he would prefer to convert the Santa Lucía air force base but airport backers, including Slim, say it is too far from downtown.
"He's a businessman, so he's defending his interests, but I'm going to be president of Mexico and I'll defend the interests of the people," said AMLO at the time.
If AMLO does go ahead and scrap the airport it could be a signal that things really are changing in Mexico.