Mexico City ( CNN ) -- Protesters marched and packed the main square of Mexico City on Sunday , slamming the candidate widely seen as the front-runner in next month 's presidential elections . Enrique Peña Nieto , the Institutional Revolutionary Party candidate , leads in polls . His party -- better known as the PRI -- ruled for some 70 years , before losing the presidency in 2000 . Demonstrators say his winning would be a step back for democracy in Mexico . `` I 'm here because I 'm really angry with what 's going on in my country . I think it 's not fair , '' said Adrian Garcia , 34 , a protester . He wore a white T-shirt with the words `` Yo Soy 132 , '' ( `` I am 132 '' ) printed on it , referencing a nascent protest group that Peña Nieto inadvertently helped to create . After students jeered the candidate at a recent campaign event , Peña Nieto dismissed the demonstrators as outsiders , dragged there by political operatives to cause commotion . Three days later , a YouTube video featured 131 students flashing their university ID cards , saying `` We are students from Ibero . ... Nobody forced us to do anything . '' The 11-minute video went viral . Posts promoting protests throughout the country on social media have used it as a jumping off point , using the phrase `` # YoSoy132 '' on Twitter and Facebook . But Sunday 's protests in Mexico City attracted more than just students -- teachers , unions and various political groups were also there . The demonstrations were timed to coincide with the last scheduled televised debate before the presidential election , which is set for July 1 . Similar , though smaller , rallies were held in several other Mexican cities . Garcia , the protester , said he voted for leftist candidate Andres Manuel Lopez Obrador in the last election . Lopez Obrador never conceded after officials declared Felipe Calderon the winner of Mexico 's election in 2006 and has been known to refer to himself as `` the legitimate president of Mexico . '' The former Mexico City mayor is running again . `` They are touching on a fundamental theme that has to do with the pretension of dominating the country through the almost absolute control of the media , '' Lopez Obrador said recently about the protesters . He and other opponents have accused Peña Nieto of receiving preferential treatment from the media since before the campaign began . The candidate , who was governor of the state of Mexico from 2005 to 2011 , has denied those accusations and said he respects the youth protests against him . CNNMexico.com and Miguel Marquez contributed to this report .
Presidential elections are scheduled for next month . Comment: Protesters rally against him , criticize coverage of the campaign .