Two of Mexico's four presidential hopefuls began their campaigns on Friday, as the country looks set to reject the party that has governed for most of the past century over corruption scandals and favor a leftist dissenter.

Opinion polls ahead of the July 1 election show Andres Manuel Lopez Obrador with a large lead, with the mainstream opposition challenger second and the ruling party candidate far behind.

Second-place Ricardo Anaya, running for the right-left coalition "For Mexico in Front", launched his campaign at just after midnight on Friday, holding a hackathon for 1,000 youths working on solutions to combat corruption and violence.

"Mexico is going to change," Anaya told the crowd of cheering young people. "This corrupt government has its days numbered."

Monica Vargas, a 22-year old literature student from the central state of Tlaxcala said she was supporting Anaya because he was listening to young people. She said many of her schoolmates had dropped out of college due to lack of funds.

"As a Mexican I feel very disappointed... we realize how rich our public officials have become, and we the people are always lagging behind," Vargas said.

Former first lady Margarita Zavala, who is in fourth place in the polls, also kicked off her campaign as an independent on Friday in Mexico City. 

Mexico saw a record number of killings last year as organized crime gangs smuggled drugs, fuel and people, while corruption scandals hit the credibility of President Enrique Pena Nieto's Institutional Revolutionary Party (PRI).

The centrist PRI has ruled Mexico continuously since 1929, except for a 12-year break when Vicente Fox and his successor led the National Action Party (PAN) to power in 2000 and 2006. Variously described as a left-winger, a populist and a nationalist, Lopez Obrador quit the PRI in the 1980s and his subsequent political career included a stint as mayor of Mexico City, one of the world's largest metropolises.

Anaya has pitched himself as a modern alternative to the unpopular PRI and to Lopez Obrador's personalized leadership.

The campaign of PRI candidate Jose Antonio Meade, who is not a member of the PRI, admits political parties are deeply mistrusted but says he is best placed to capture the mood.

For many voters, July 1 will be about rejecting either the corruption of the ruling party, or Lopez Obrador, said PAN Senator Ernesto Ruffo.

"This is an election not for, but against," he said.

[Cover Photo: Ricardo Anaya, presidential candidate for the National Action Party (PAN), greets supporters during his kick-off presidential campaign in Mexico City, Mexico, March 30, 2018. /Reuters Photo]