In recent years, Leo Zuckermann has often argued that candidates matter more than is often realized in Mexico, pointing to, among other elections, the PRI's defeats in Guerrero and Baja California Sur. I haven't been following the Michoacán election too closely, but the news that, according to Reforma, Cocoa Calderón is now leading the governor's race sounds like more evidence of that. She was, after all, in third place a month ago, 13 points off the lead.
Alternatively, the poll could be crap. We'll know here in about 10 days.