On July 8, Lopez Obrador, often referred to as Amlo (his initials), attracted a crowd up to half-a-million people who poured into Mexico City's main square, known as the Zocalo, proving that the best political card in his hands right now is his ability to mobilise the masses.
For hours the world's second-biggest square (after Tiananmen in Beijing) was coloured with yellow, the colour of Lopez Obrador's Democratic Revolution Party.
It was an outpouring of public support similar to the Orange Revolution that gripped Kiev after disputed elections there in 2004.
In a country of 103 million people - at least half of whom are poor and 18 million of those live in extreme poverty - most of the protesters have no health services, no education and no land and so feel they have no future and no dignity. They say they have nothing to lose because they have never gained anything. And they are simply fed up.
"With our blood, with our souls, we will defend Lopez Obrador"
Chant from Amlo supporters in the Zocalo
I recently visited one of Mexico City's many poor neighbourhoods; everywhere I went I could smell the sewage.
People here earn less than two dollars a day.
Of course, compared with other countries I have been to, it is not that bad. However, this is Mexico, where there should not be any poverty at all.
The country is rich in resources including oil, gas and uranium, but has one of Latin America's worst records on wealth distribution.
Had Lopez Obrador won the presidential elections, he would have surely won by a very tight margin. He would then have had both chambers of government against him and he would have faced a country divided and difficult to rule.
It is quite possible that these challenges would have been too great to face and his electoral promises would end up too remote to reach.
Lopez Obrador is a former mayor
of Mexico City
He, or anybody else, is unlikely to make rapid effective changes that would make the poor less poor.
He would have therefore ended up disappointing the same masses that support him now, and even though he has still not reached the presidency, these masses believe in him more than ever.
They hang on to him as a symbol of resistance and hope.
He gives them a dream that nobody else has given them before, although some might say the leader of the Zapatista Liberation Army, Subcomandante Marcos, has been that symbol.
But Marcos does not seek power and he does not come from within the establishment, as is the case with Lopez Obrador.
After all the voting, political manoeuvring and legal argument, it may be that Amlo has no option but to go against the current if he wants to have a political future.
If he were to accept the result of the elections, he would probably lose his popularity and face a long and slow drift into political death, simply because the masses cannot accept the status quo.
If he is to disappoint them, then Marcos would be the next person to whom they would turn, although he seems to attract fewer and fewer Mexicans to his rallies.
"This is idiot is making fun of Mexico"
Slogan on an anti-Calderon banner
Lopez Obrador manifesto is not anti-imperialist and he would not be likely to make radical changes towards the left.
Despite this many of his supporters want an anti-US government in Mexico, want the whole package of radical changes seen in countries such as Venezuela and Bolivia. They do not seem to realise that Amlo was going to be none of the above.
Plunging into the human sea in the Zocalo after the rally, I could see great anger in people's eyes. Some scared me. They were shouting: "With our blood, with our soul we will defend you Lopez Obrador."
Many said, or rather screamed at me: "We will not tolerate the rich stealing our country's resources and leaving us poor for ever. It is time for the poor to be on top and the rich to be in the bottom."
Felipe Calderon celebrated -
then went on holiday
Some cried, some were hysterical; some grabbed my Aljazeera microphone and shouted irrational, hardly understandable words to the camera.
They even yelled at me: "liar", thinking I was a Mexican journalist not telling the truth about them.
Whether or not Lopez Obrador proves his point about the alleged fraud committed in the elections does not seem to matter that much any more.
The 14 million voters who chose him as their candidate might grow in number now that someone is standing up against the system through which 300 powerful families have always ruled Mexico.
During the rally on July 8, the official winner in the elections, Felipe Calderon from the National Action Party, was relaxing in Cuernavaca, a summer town where rich Mexicans typically have their holiday or weekend homes.
Watching the Zocalo turn yellow, he might have been alarmed. For me it was like the Yellow River in China which floods regularly.
If the Zocalo keeps flooding then maybe Calderon ought to spend less time in Cuernavaca and watch out for wider floods across the country, which could end up at his doorstep sooner than he thinks