Mexico’s election season is underway — and dozens of candidates have been brutally killed by unknown assailants in an apparent attempt to control the country’s political future.

Since September, 113 politicians, including 43 candidates running for office, have been killed, according to Etellekt, a Mexican political consulting agency. And earlier this month, three female political candidates were shot dead in just 24 hours.

They include people like Pamela Terán, a member of the Institutional Revolutionary Party, or PRI, who was running for municipal council in Juchitán. She was killed on June 2 while leaving a restaurant in Oaxaca; her father and a photographer were also killed.

Last Friday in Piedras Negras, congressional candidate Fernando Purón was shot in the back of the head while taking a selfie with a supporter following a debate with his rivals. Purón had also been an advocate for organized crime reform.

The wave of violence precedes Mexico’s presidential election, which is set to take place on July 1. But Mexicans will also head to the polls to elect more than 100 members of the country’s Senate and 500 members of the Chamber of Deputies, Mexico’s house of representatives. It’s set to be the largest election in the country‘s history, with reportedly more than 3,400 seats open at the local and state level.

But since the violence began in September, hundreds of candidates have pulled out of races out of fear of being targeted. The uptick in violence indicates how risky it is to run for public office in a country known for its endemic corruption and high rate of crime. And it shows no sign of abating.

Last year, Mexico saw the highest number of homicides in the country’s history, with 29,168 total homicides according to preliminary government data.

“It’s very likely that the number of homicides [in 2017] is actually around 32,000,” José Antonio Polo, director of the public safety watchdog Common Cause, told NPR. “So the bad news isn’t that the current number is the highest ever — it’s likely to get even higher.”

Mexico’s leading presidential candidate has made fighting corruption a central part of his campaign

The frontrunner in the upcoming presidential elections is Andrés Manuel López Obrador. He’s running for the recently formed, left-wing Morena party and has promised to advocate for reform against the country’s widespread corruption; polls show he’s been in the lead for months.

López Obrador’s three rivals include conservative candidate Ricardo Anaya; a member of the governing PRI party, José Antonio Meade; and independent Jaime Rodríguez. All four are reportedly not fans of US President Donald Trump; at the third and final presidential debate earlier this month, the candidates called for a strong relationship with the US but also made it clear that they would stand up to Trump’s aggressive bullying tactics.

Though the upcoming presidential election might be getting the most attention, it’s actually quite rare for high-profile presidential candidates to be targeted and murdered, said Eric Olson, the deputy director of the Wilson Center’s Latin American program.

Olson told me that most organized crime groups in Mexico target candidates at the local level, so people running for lower-profile positions are at greater risk.

“Presidential candidates are vulnerable, but they’re surrounded by people and there’s constant attention, so only in the most extreme and unusual situations would a criminal organization go after a presidential candidate. They’re more concerned about local authorities,” Olson continued.

So far, BuzzFeed News has reported that more than 600 people have pulled out of races.

But if López Obrador secures the presidential seat in July and manages to carry out his political promises, Mexicans could potentially see wide-sweeping reforms.

“No one should be worried if I use the word ‘radical,’” López Obrador said at a rally in Jiutepec. “I use radical in the sense of coming from root. Because I want to uproot corruption and injustice.”

Correction: An earlier version of this article misstated the party affiliation of the presidential candidate Andrés Manuel López Obrador. He is a member of Morena, not an independent.