FILE PHOTO: The left frontman Andres Manuel Lopez Obrador of the National Regeneration Movement (MORENA) speaks during a conference organized by the Mexican Construction Industry Association in Guadalajara, Mexico March 23, 2018. REUTERS / Henry Romero  The centrist PRI has Mexico ruled uninterruptedly since 1929, with the exception of a twelve-year hiatus, when Vicente Fox and his successor brought the National Action Party (PAN) to power in 2000 and 2006.
Both the PAN and the PRI preferred the opening up of the economy to more foreign investment and close relations with the United States.
Lopez Obrador was described in the 1980s as a left winger, populist and nationalist. In the subsequent political career he was mayor of Mexico City, one of the world's largest cities. Since his first inauguration in 2006, he has been in constant opposition.
He says only he can eliminate deep-seated corruption in the traditional parties. At the same time, he promises to amend the constitution if he will end immunity for sitting presidents and hold regular referendums on key issues, including one every two years to continue his six-year term.
"We Mexicans now see that there are definitely two alternatives ahead of us," said Tatiana Clouthier, a high-ranking member of the Lopez Obrador campaign on Thursday: more of it, or a government that will spread the wealth further.
In second place is former PAN chief Ricardo Anaya, whose coalition is made up of center-left parties that were once allied with Lopez Obrador. He has presented himself as a modern alternative to the unpopular PRI and the personalized leadership of Lopez Obrador.
For many voters, July 1 will be about either rejecting the ruling party's corruption, or Lopez Obrador, said Ernesto Ruffo, a PAN senator who was the first politician to take control of a state government in 1989 Torn PRI.
"This is not a vote for, but against," he said.
Only Anaya, said Ruffo, offered a vision of the future.
The campaign of PRI candidate Jose Antonio Meade, who is not a member of the PRI, acknowledges that political parties are deeply distrustful, but says that Meade is best able to capture the mood.
Meade says that Lopez's beating in the private sector, many of the 64-year-old Lopez has corrupted investor sentiment.
"If there is investment, there are jobs," Meade told the Mexican radio on Thursday. "If there are jobs, we fight poverty."
Additional coverage by Dave Graham; Arrangement by Dave Graham and Paul Tait