PRI started out as a socialist party and slowly evolved into an entrenched ruling party with no real ideology other than crony capitalism, embedded corruption, and rent-seeking. PAN pretend to offer an alternative based on deregulation and open markets, and wound up as much in bed with the drug cartels as PRI (if not worse). If AMLO gets a run at it, Mexico will be back to where they were at square one before PRI's reboot: "revolutionary" Marxist socialism. Then the cycle will repeat itself, with no substantial improvement in sight.
It turned out PAN’s plan to make Mexico “better” involved moving tens of millions of their criminal and peasant underclass to the USA. No wonder Fox has been so utterly deranged that his “plan” was discovered and that he’s been attacking President Trump so relentlessly.