While this important position corresponded to the PRD - the PRI reneged on an earlier agreement (see background here and here) - the three main parties PRI, PAN, and PRD will instead take turns the last year of this session, while PRD will head the coordinating junta.
A year ago, when a deal had been made that the PRD would preside both the junta and the directorate for the entire session, I wrote:
The coordinators of the parties in congress agreed to a deal where PRD will get to preside the two organs, though a special vote of 2/3 majority will be held where the stipulations of the Organic Law regulating Congress will simply be "set aside" for that year. PRD will simply have to take their word for it, that this will actually come to passAnd guess what happened? PRI reneged on this promise.