UPDATE (3 July): Good analysis of the Bolivian result at Boli-Nica.
Mexico is not the only country having an election today. See Miguel’s notes about the referendum and constituent assembly election in Bolivia. Also our previous exchanges about the funky two-vote, two-tier parallel closed-list limited-seats/[almost] “every party gets a seat”* electoral system being used today. (Miguels’s posts are: “Assembly Candidate Lists” to which I commented back in April, and Miguel’s response, “Brief review of constituent assembly electoral system,” which also has an image of a ballot).
* I said it was funky. Just to tie today’s elections together, Bolivia’s lower tier rule is the same as the Mexican Senate’s lower tier (also used in Bolivia’s own senate). However, the upper tier is just weird: departmental-level allocation of two seats to the leading list, and one each for the remaining parties till the district’s seats are exhausted. Unless that gets down into parties with less than 5%… I told you it was funky! (And please don’t call it either “mixed-member” or “PR”! Labels matter.)
UPDATE (in response to Miguel): I changed the “limited nominations” in my original (whimsical) name for this electoral system to “limited seat” for accuracy (see comments below for more) and also becuase it has a nice parallel (so to speak) with the concept of a “limited vote” system (defined as a nominal-vote system wherein voters get to vote for more than one, but less than M candidates, where M is the number of seats in the district and the top M vote-winners are elected). The Bolivian rules that this discussion refers to say that the plurality party wins more than one seat (and likely more than proportional seats), but less than M seats. Hence “limited seats,” which I would consider a variant of list plurality, just as I would consider the limited vote a variant of nominal plurality. (The system in question would also be “limited nominations” if the party could place on its list only as many candidates as it could win, were it to get the plurality of votes, which apparently is not the case here.)