Arce

“The entire social history of Mexico is narrated through corridos,” said José Manuel Valenzuela Arce, a sociologist in Tijuana.

His supporters had clashed with followers of his rival, current President Luis Arce, on several occasions earlier this year.

The faction said it held President Arce's government responsible.

Both he and Arce have groups of loyal supporters willing to take to the streets - and in some cases engage in street brawls - to show their backing for their candidate.

Arce condemned violence in politics and pledged an investigation.