Running for public office in Mexico has long been perilous, with threats, assaults and sometimes outright killings by criminal gangs, political rivals and other opponents, but this season is one of the worst in recent years with at least six candidates killed since February 2013 and another wounded in an attack that left her husband and an assistant dead

Party and campaign officials have also been assaulted, their family members targeted and sometimes killed as well. As nearly half of Mexico’s states prepare to hold local elections, the outbreak of violence has proved an embarrassment for the new government of President Enrique Peña Nieto, who has promised to control violence and has sought to portray the country as on the mend from wanton killings. While the Peña Nieto administration promised to take steps to protect voters, opposition leaders have called on the president to put the army in the streets in some states to ensure peaceful voting proceedings, a common practice in Mexico. “We are in the midst of the most violent elections in our history,” said José María Martínez, a member of a conservative-leaning opposition party and president of the special electoral commission of the Senate. “This is not the country that any Mexican deserves.” Martínez’s National Action Party, which lost the presidency in 2012, is one of the two main opposition parties that have threatened to break a collaborative pact with Peña Nieto if the elections are neither fair nor safe. The motives for many of these attacks, from which no major party has been spared, remain unclear. Local investigations of crimes, even killings, are notoriously haphazard and thin. The number of cases, meanwhile, continues to grow. Recently, Nicolás Estrada Merino, leader of a state branch of the leftist Party of the Democratic Revolution, was found shot to death in a sugarcane field in the southern state of Oaxaca. Isaac López Rojas, a candidate for deputy mayor from the small, leftist Cardenista Party in the coastal state of Veracruz, was kidnapped and killed, also in June 2013. A few days earlier, in the border state of Chihuahua, a mayoral candidate from the governing Institutional Revolutionary Party, Jaime Orozco Madrigal, was found dead after being forcefully taken from his house. Newspapers have reported a number of candidates dropping their campaigns out of fear, and news channels have featured interviews with bloodied and bruised party members speaking after unexplained attacks. The violence presents a problem for Peña Nieto, who has sought to highlight the country’s economy and court foreign investors while playing down the persistent trouble with crime and offering vague plans on how to address it. Analysts say that the recent electoral violence has highlighted the extent to which Mexico has failed to make progress in confronting the impunity that allows attacks during each voting cycle. “It would seem like we are in the postrevolutionary years,” said Jorge Chabat, a drug and security expert at CIDE, a Mexico City research group, referring to the period after the revolution of 1910, when the number of political assassinations was particularly high. “I can’t remember so many candidates getting killed before an election.” These acts “disturb the peace,” said Leonardo Valdés Zurita, president of the Federal Electoral Institute, during a council meeting in which he asked for a minute of silence to honor the victims. Most of the killings have taken place in small towns, which are especially unprotected and vulnerable to drug and organized-crime groups seeking to expand their turf. “That’s where the organizations fight for control of plazas, of routes,” said Eric L. Olson, director of the Latin American program at the Woodrow Wilson International Center for Scholars in Washington. “They often depend on control of local mayors and local officials to ensure that they are protected.” Still, the motives are murky. After the killing of a campaign coordinator’s teenage son in Sinaloa State, the authorities denied any political motivation, citing the boy’s possible involvement in crime as a theory. The kidnapping and killing of a candidate in Veracruz, state officials also insisted, was unrelated to his political aspirations. Some analysts and members of the Institutional Revolutionary Party warned about over-blowing the violence, which is common in elections but usually does not interfere with balloting. “The conditions to carry out the elections do exist,” said Patricio Martínez, a senator from the party. “They’re not perfect; perfect is only left to God.” But some observers remain unconvinced. “A state that cannot protect its candidates,” said Ernesto López Portillo, director of the Institute for Security and Democracy, a research group in Mexico City, “is a state that cannot protect democracy.”