– Voter discontent in Mexico is high, and a debate rages over how best to send the political class a message of disgust in Sunday’s midterm elections.

Some academics, artists and protesters urge the nation’s 83.5 million voters to nullify or deface their ballots, even holding up signs along Mexico City’s main boulevard calling for such action.

Others exhort voters to take advantage of a newly opened electoral system and shun traditional party politicians, electing an independent for the first time to govern one of Mexico’s richest states.

Voters — many of them in a foul mood — will replace the 500-seat lower house of Congress, select nine out of 32 state governorships, and elect legislators and mayors in 16 states.

Once ballots are counted, the midterm election could allow President Enrique Peña Nieto’s ruling party and allied parties to maintain a shaky majority in Congress until his term ends in 2018.

A spike in violence, some by criminal gangs but mostly by angry teachers in Michoacan, Guerrero, Oaxaca and Chiapas, threatens the vote. Protesters have blocked highways, blockaded gas stations and set fires at election facilities.

At least seven candidates have been gunned down.

Despite the violence, signs are rising that voters are disaffected not just because of a sluggish economy, corruption scandals and unsettling problems with criminal mayhem. A growing number question the political system itself.

“Mexican elections are an absolute farce,” actress and writer Ofelia Medina said in Spanish in a video posted last month on YouTube. “No party has any ethics at all.”

Medina and scores of other prominent figures support the campaign to deface ballots rather than filling them in.

Political analyst Denise Dresser, who supports the campaign, said that by casting nullified ballots, voters would send a message about “an electoral system that functions very well for the parties but very poorly for the citizenry.”

The “null vote” campaign has gathered enough steam that it’s been debated at the National Electoral Institute, which runs elections. It says nullified votes in 2009 rose to 5.4 percent of ballots cast.

“There are a lot of citizens, like me, who don’t trust any of the political parties,” said Jose Antonio Crespo, a historian and political analyst at the Center for Research and Teaching of Economics.