I'd like to republish a post Miguel Centellas from Ciao! wrote about the Bolivian electoral system. I've been wanting to do something similar, but Miguel has done it so much better and sooner. The post is brief, yet it is a good overview using some technical terms which are important to understand the system.
The reason I post the entire article on MABB is because, in addition to provide this important information to my visitors, I'd like to have a record of it for my personal use as well.
Brief review of constituent assembly electoral system
By Miguel Centellas (Ciao!)
This is in response to Matthew Shugart's comment/question from this previous post on Bolivia's constituent assembly election. I now have a free moment to give a slightly better (i.e. clearer) account of the upcoming election. First, some background.
Since 1994 (first used in the 1997 election), Bolivia has used a mixed-member proportional (MMP) electoral system. That means that roughly half the lower house (the House of Deputies) are elected in first-past-the-post single member districts, while the rest are elected from party lists in nine multi-seat districts (the departments) using proportional representation. (For you electoral system nerds, specifically D'Hondt PR w/ a 3% electoral threshold.)
The single-seat districts are known as distritos (circunscripciones) uninominales in Bolivia. The department-wide districts are known as distritos (circunscripciones) plurinominales.
In the constituent assembly, the compromise (after several different proposals) was to elect FIVE delegates from each department (cf. distrito (circunscripción) plurinominal) & THREE delegates from each distrito (circunscripción) uninominal. Of course, it's not "literally" a "uninominal" district if it elects more than one delegate, but here we mean that they correspond to the electoral districts used to elect uninominal deputies during general elections. For reference, see the Ley Convocatoria.
As for the electoral formula. The ballot for the constituent assembly will resemble the ballots in general elections. This is good, since voters are familiar w/ the structure.
Here's a sample ballot (from La Paz). The top part is for the "plurinominal" (department-wide) candidate lists; the bottom part is for the "uninominal" candidate lists. Each voter will cast one vote for each portion of the ballot (voters can cross-vote). Essentially, voters are voting for two parallel sets of lists, not for individual candidates.
Seats will be awarded using a pretty simple formula. In the "uninominal" districts, the list w/ the most votes wins two seats; the list w/ the second-most votes wins the remaining seat. No other lists win seats. In the "plurinominal" districts, the list w/ the most votes wins two seats, w/ one seat each for the 2nd, 3rd, and 4th place lists. In the case that the 4th or 3rd place lists don't win at least 5% of the vote, the top two parties will split up the remaining votes. See Article 14 in the Ley Convocatoria.
All in all, I think this electoral system is pretty simple, and not an entirely radical change from the current MMP system. I also think it might correct for some of the problems of first-past-the-post uninominal districts (where many candidates win w/ only 18-22% of the district's votes).
NOTE 1: Yes, I realize that the ballot includes the photos of individual candidates, so it seems that voters are actually voting for "individual" candidates. But the photo corresponds only to the titular candidate on each list. So the department-wide UN list in La Paz is headed by Samuel Doria Medina. But you'll notice that there are three other names below his. Also note that different parties have presented a different number of candidates on each list. Based in large measure on how many maximum seats they hope to win. Though I'm not sure why any list includes five names, since even in a blowout, no party could possibly win all five seats.
NOTE 2: Eduardo corrects me that the uninominal districts are usually referred to as circunscripciónes uninominales (not distritos).