Members of a radical Mexican teachers union broke into or blockaded electoral offices in the southern state of Oaxaca on Monday amid threats to block this weekend's midterm elections.
National Electoral Institute head Lorenzo Cordoba said that teachers destroyed furnishings at two of the offices and that the union's actions could force authorities to move polling places to alternate locations for Sunday's voting.
Teachers blockaded several other offices, causing the electoral institute to suspend work in parts of Oaxaca. Teachers burned about 13,500 ballots that had already been cancelled, and an unidentified group in the town of Juchitan stole almost 10,000 ballots that electoral officials said are numbered and can be cancelled so they won't be used.
Mr. Cordoba said the situation in Oaxaca probably represents the biggest threat to the election, even more than drug cartel violence that has marred past elections in Mexico.
"Given today's events, I would say our area of biggest concern is Oaxaca," he said. "Organized crime hasn't tried to block the elections, but some social movements have."
The radical teachers movement has built a reputation for long strikes and takeovers of public spaces, like the 2006 uprising that sought the ouster of the Oaxaca state governor. Teachers led a five-month takeover of colonial Oaxaca city, the state capital.
The teachers, some of whom inherited their teaching jobs from relatives rather than proved their skills in the classroom, vigorously oppose a 2013 education reform that requires competitive testing for teachers. The union says those tests don't really measure teaching skills and don't take into account the special knowledge needed to teach in Indian and rural areas.
Over the weekend, the government appeared to bow to their demands by suspending planned tests, without stating what many people suspected was the real reason: persuading the teachers union to allow Sunday's elections to go forward.
The Education Department said only that "given new elements that should be taken into account in (teacher) evaluation ... the previously announced test dates will be indefinitely suspended."
Because teacher testing was considered the central point of the hard-fought reform of Mexico's woefully under-performing schools, the announcement drew widespread criticism.
"By suspending teacher evaluation, the federal authorities have given up the chance to advance toward quality education," a group of 20 civic groups said in a statement. "And what is worse is that it was done in the face of blackmail," it added, referring to the teachers' threat to block the elections.
Mexico has seen drug cartel violence mar elections in the past. In 2010, the leading candidate for the governorship of the border state of Tamaulipas was slain by cartel gunmen. So far this year's campaign for congressional seats, nine governorships, and hundreds of mayorships has been marred by lower-level killings, including the deaths of two small-town mayoral candidates.
Cordoba said drug-gang violence and crime remains a concern, forcing electoral workers in some places to operate only in daylight and in teams. Workers sometimes leave their electoral institute caps and other identifying insignia behind and work in plain clothes.
But he said threats to block elections, which apparently started with the parents of 43 missing college students in southern Guerrero state who said they wouldn't allow elections until their children were found, has become a greater potential danger.
"I think we run the risk, as a society, that the threat to block elections is becoming a universal practice, as a way to press demands," Cordoba said.