Mexico is not burning, the country’s Interior Minister Miguel Ángel Osorio assured citizens last month in response to pre-election violence that saw at least three candidates murdered by mid-May. But flaming government buildings and a mounting body count have defied Osorio in the run-up to Sunday’s midterm elections, in which 500 congressional seats and nine governorships are at play.

Since Osorio’s declaration, at least four more candidates from various political parties have been gunned down as dozens of criminal gangs coerce candidates in a battle to control local terrain and drug-trafficking routes. At least 20 additional candidates have been intimidated out of the running. The drug-fueled violence has coalesced in recent days with violent protests in Mexico’s southern states, as teachers opposed to education reform, joined by parents of the missing 43 students in Guerrero state, have blocked highways, sabotaged would-be voting stations and burned thousands of ballots.

“These are the dirtiest elections since the advent of democracy in Mexico,” Raúl Benítez, a security expert at the National Autonomous University of Mexico, told Reuters this week.

Simmering grievances that arose out of 2014 education reforms have spurred a section of Mexico’s teachers union, the National Coordinator of Educational Workers (CNTE), to intensify its protests this week. The group has ransacked government buildings and faced off against police in the southern states of Guerrero and Oaxaca — all with the hope of disrupting elections. CNTE on Wednesday won a partial concession from the government of President Enrique Peña Nieto when it agreed to suspend teacher evaluations, a key provision of educational reform.

But that has done little to douse protests. Recent demonstrations, Mexico analysts say, are a result of an endemic disillusion in Mexico’s southern states with the corruption that steers the country’s main political parties, including Peña Nieto’s governing Institutional Revolutionary Party, or PRI.

Just last week, Peña Nieto signed an anti-corruption measure that will assign a special prosecutor to rein in corruption and will bolster oversight of public officials. That includes subjecting politicians to audits of public finances. Critics, however, pounced on the measure for having few teeth. Elected officials accused of corruption, they point out, will continue to benefit from immunity from prosecution. And the measure does not tackle the problem of low rates of prosecution for corruption.

Sunday’s elections, in which 300 mayoral seats are also up for grabs, represent Peña Nieto’s biggest political challenge since winning office in 2012 with the promise of economic reforms and restoring peace after drug-related violence claimed nearly 60,000 lives under the six-year presidency of Peña Nieto’s predecessor Felipe Calderón. Under Peña Nieto, violence has dropped only modestly. In 2013, his first year in power, there were 22,732 homicides in Mexico — about a 12 percent drop from Calderón’s last year in office — according to the country's National Statistics Institute.

Peña Nieto has also had to navigate damaging scandals. The most serious has been the case of the missing 43 teaching college students. The leftist student activists were abducted last September in Guerrero at the hands of local police and politicians, according to investigative reports. They remain missing and are presumed dead. Just weeks after they disappeared, Mexican media revealed that a government contractor — part of a consortium that was granted a billion-dollar, high speed train contract — built and financed a house for Peña Nieto and his wife in Mexico City’s upscale Lomas de Chapultepec neighborhood.

Despite a tumultuous two years in power, polls indicate Peña Nieto’s PRI is expected to eke out a small majority in Mexico’s lower house of Congress on Sunday — at least in part because opposition parties are divided and not immune from voter anger. But polls also show that the PRI could lose some of its power in several states in the face of corruption and a sluggish economy.

That ever-dwindling confidence in the ruling elite was on full display in Guerrero this week. On Thursday in the state capital of Chilpancingo, supporters of the missing 43 students and their families joined CNTE members and other protesters as they vandalized the PRI’s local headquarters.

“Narcogovernors,” read graffiti sprayed on the walls, according to the news website Animal Político. “On June 7, not one more vote for thieving parties.”

With wire services