Running for political office in Mexico can be a life-threatening feat. At least four candidates and politicians have been killed ahead of this Sunday’s elections in Mexican states, as drug cartels seek to gain influence over local officials. Politicians murdered in the last month include a party leader in Oaxaca, mayoral candidates in Veracruz and Chihuahua states and a campaign manager in Sinaloa. “Political assassinations won’t end anytime soon,” says Jorge Chabat, a political science professor at the Center for Economic Research and Teaching, a Mexico City-based university. “It’s very probable organized crime groups are trying to prevent some people from gaining office, either because they think they’ll act against their group’s interests, or because they think they’re aligned with a rival gang.” Interior Minister Miguel Angel Osorio told reporters last week that the government will “thoroughly investigate” the killings and “seek out solutions and clarifications.” Pre-election murders aren’t a novel concept in Mexico; in 2010, gunmen killed at least 10 standing mayors and shot dead Rodolfo Torre Cantu, the leading gubernatorial candidate in Tamaulipas state. Despite this, the Interior Ministry reported last April that drug war killings dropped 14% in the first four months of new Mexican President Enrique Pena Nieto‘s administration, compared to the same period a year later.