UPDATED:
It has now been reported that the Mexico City police estimated that there were 1,100,000 people attending the "March for Democracy" led by presidential candidate Andres Manuel Lopez Obrador in Mexico City's central square, the Zocalo.
By the way, police earlier estimated that the marchers, who assembled at Mexico City's famed Museum of Anthropology to march about 14km to the Zocalo, already numbered about 300,000.
So we may HAVE HAD OVER a MILLION MARCHING to protest what they believe (and I think, believe correctly) to have been massive manipulation and fraud in the presidential elections of Mexico.
Will Mexico's engaged populace help us stop the defrauders?
As someone kindly reminded me below, the march has been called to demand that the election be recounted "Vote by Vote," "Ballot Box by Ballot Box."
The federal body charged with supervising the campaigning process and the initial count, IFE, is accused by many (most prominently Lopez Obrador himself)) of having acted improperly on many, many counts.
For example, the count announced last week which declared governing party right wing candidate Felipe Calderon Hinojosa the victor with 0.58% was actually based on a count of the already-counted tally sheets from each of the (presumably) sealed ballot boxes. That's a margin of victory of a little over 243,000 votes. However, there could be over 900,000 or more votes which were uncounted and labeled "inconsistent."
In several samples, the ballot boxes were unsealed (officially) and recounted, and the "inconsistent" votes turned out to strongly favor Lopez Obrador.
Lopez Obrador (or AMLO, from his initials) has submitted a 900 page challenge and complaint to the court which now has authority under the Mexican Constitution, known by its Spanish acronym as the TEPJF (Tribunal Electoral del Poder Judicial de la Federacion). This is the body which is charged with actually certifying the election, and has broad authority which it has used at times to both order reviews as well as even annulling elections which it deemed improperly administered.
Anyone monitoring this event please add comments below as necessary to update and correct information.