For those interested, who are the PRI, PAN and PRD/PT parties? Just so we know the players. Thanks.
PRI (Partido de Revolution Insititucional) was the ruling party since the Revolution. It has no real ideology except power, bit tends to lean left because it has always bought the vote (so giveaways are very popular).
PAN (Partido Accion Nacional) is Vicente Fox's party. It is a close as a Conservative you will find, but it resembles the Murtha/Pelosi/Dean wing of the Democrats (as opposed to Leiberman).
PRD (Partido de la revoluton Democratica) is the somewhat Lefty Party -- Like their version of the Democrats but more like the Socialist Labor Party.
PT (Partido Trabajo-Workers Party) is flat-out Communist.