Normally calm prevails before Election Day in Mexico, as campaigning is banned in the three days before the vote. This year protests by militant teachers and radical social movements, particularly in four southern Mexican states, have become increasingly strident, with demonstrators blocking gas stations, thereby disrupting economic activity, and threatening to disrupt Sunday's balloting. Authorities say this is the first time ever in Mexico that protests have threaten to disrupt the elections. To promote its cause and to not have to depend on the corporate media, the powerful Oaxaca teachers union has its own community radio station that broadcasts its message. Clayton Conn reports from Oaxaca.