El Bronco, the country's first independent governor, takes office in Nuevo Leon and amid barbs with Andres Manuel Lopez Obrador — a hint of both men's anti-system presidential aspirations ahead of 2018 election.
Margarita Zavala's unexpected announcement came one week after a midterm election in which the National Action Party suffered its worst showing at Mexico's polls since 1991.
The scandal-ridden Green Party said it had nothing to do with supportive messages sent by Mexico's national soccer coach and others, which is illegal under electoral rules. Rival parties cry foul.
Indie candidates also stormed to victory in key races in Jalisco, while the upstart leftist Morena movement made gains in Mexico City and in Congress. One man is killed in Guerrero.
A Mexico City newspaper said as many as 70 political attacks have occurred since February, as Mexico prepares to elect 500 lawmakers, nine governors, and hundreds of local office-holders.