A trenchant critic of the ruling elite, Lopez Obrador would become Mexico's first left-leaning leader for decades if elected on Sunday, breaking the stranglehold of the ruling Institutional Revolutionary Party (PRI) and its conservative rivals.
Final polls show the former Mexico City mayor with a lead of more than 20 percent over his presidential opponents, PRI candidate Jose Antonio Meade and the second-placed Ricard Anaya of the center-right National Action Party (PAN).
Combining campaign pledges with a whistle-stop tour of Mexican political history, Lopez Obrador promised a "radical" government that would end unearned privilege, stamp out impunity and imbue the country with "moral authority."
"The country will be cleansed," Lopez Obrador said on Wednesday inside Mexico's largest soccer venue, the almost full 87,000-seater Azteca Stadium. He promised to "pull up by its roots the corrupt regime" he blames for chronic violence and poverty.
Dressed in a dark suit and an open-necked white shirt, he compared his movement to Mexico's great social upheavals, including the 1910 revolution, and said a new era was at hand.
"It's going to be a peaceful, orderly but deep transformation," Lopez Obrador said.