Tension continues to build in Mexico ahead of Sunday's vote, particularly in four southern states where violence has erupted. The combative teachers union and local organizations are calling for a boycott of Sunday's elections. In Oaxaca, the 75,000 strong combative teachers union Section 22 has been in the forefront of the anti-election protests, with actions such as blocking the international airport. The resentment of political parties and the governing elite runs deep and coupled with rejection of recently enacted neo-liberal reforms, could likely mean an escalation of tensions between now and election day. In fact, teachers union activists expect a more violent response to their protests by authorities. Clayton Conn reports from Oaxaca.