AMLO's Santa Ana reference

Among the various themes that AMLO constantly repeats in his campaign appearances is that a return of the PRI to the Mexican presidency will be equivalent to the return of 19th-century dictator Santa Ana.

Beyond my basic concurrence that the return of the PRI will likely be a very negative development for Mexico's democracy, a question: 

If PRI's return is like Santa Ana's - then how can at the same time PRI and PAN be "all the same," as he constantly repeats? And why, then, his ardent opposition to PRD-PAN state-level electoral alliances that sought to prevent PRI's return? 

AMLO's media coordinator César Yáñez, who still owes the AMLO interview he promised me, may send a reply to aguachileblogger@gmail.com