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Political Change in Mexico, 2012 - 2018

The map below shows the percentage increase in votes for congressional candidates running on Andres Manuel Lopez Obrador's ticket (PRD in 2012, Morena in 2018). Beyond Lopez Obrador's resounding 53% victory in the 2018 presidential election, his party's coalition dominated downballot races and captured a legislative majority.

Initial examination of the map suggests that Morena garnered its biggest victories in areas that were not existing bastions of control for either the PAN or PRI, and that areas where the PRD was dominant in 2012 did not necessarily equate to easy victories for Morena candidates. Indeed, there are few electoral sections where Morena succeeded in "flipping" a PRI bastion, despite the suggestion that Morena's success was the result of priista defections. There were only 9 sections where the PRI won upwards of 70% of the vote in 2012, and Morena won more than 60% in 2018 (in 14 more sections, where the PRI won 60% in 2012, Morena equaled that result in 2018). 

The map is interactive: more information about an electoral section can be obtained by hovering or selecting the region. Though it may be slow to load, it can also be zoomed to regions of interest, and the picture often becomes clearer from closer up.

Helpful information about the map's symbology, methodology, concepts, and a legend can be found at the bottom of the page.


The map's assorted circles and arrows indicate changes in outcomes for parties other than Morena. In particular, I was interested in the behavior of sections where one of the parties had previously captured 70% or more of the vote ("bastions"). For purposes of this map, I deemed a bastion to be "flipped" if Morena captured 60% of the vote there, and "lost" if the previously dominant party experienced a 50% or greater reduction in vote percentage there. Morena did not flip any PAN bastions.

The underlying cloropleth map is coded by the difference between vote percentage for the PRD candidate in 2012 and the Morena candidate in 2018. In some sections, the difference was greater than 50 points, though for purposes of visualization the color scale stops at 50. Those sections are marked with a red star. 

Other Notes

Data for some sections was unavailable or could not be rendered due to changes in the electoral map. Sections where zero total votes were recorded in either 2012 or 2018 are gray, and do not react to user input.

Rather than plotting presidential voting data, which I have done elsewhere, this map looks at votes for congressional deputies. Because congressional terms were short (three years with no reelection*) they offer a good means of visualizing the strength of a party's brand and its machinery since candidates were often unfamiliar. The relative frequency of congressional elections also makes them prime fodder for analysis; a 2015-2018 version of this map should be available soon.

* Starting in 2021, members of the lower house of congress will be eligible for reelection.

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