Puerto Rico – that most ambiguous part of the United States – uses an electoral system equally imperfect as that fraught relationship. Puerto Rico's bicameral legislature (consisting of a Senate and a Chamber of Representatives) is largely elected by first-past-the post (FPTP); it is made distinctive from other US legislatures by the modest number of list seats elected at-large. These seats are chosen through a semi-proportional method, the Single-Non-Transferable Vote (SNTV). Though eleven at-large representatives are elected from each house, voters may choose only one candidate. The problem with this particular hybrid becomes obvious when examining the 2008 results. In the Senate, the victorious New Progressive Party won 47.7% of the total district vote, and all 16 district seats, while the unlucky Popular Democratic Party earned no seats on 47.1% of the vote, a truly blatant unrepresentative result. The relatively fair result of the at-large seats, in which the New Progressives won 6 seats versus 5 for the Popular Democrats did nothing to mask the outsize seat total (over 80%) earned by the winning party. The Chamber of Representatives was little better, the New Progressives nabbed over 80% of district seats, while splitting the at large seats.

Puerto Rico has a mechanism that attempts to ameliorate some of these problems. Article II, Section VII of the Constitution of Puerto Rico requires that additional members from opposition parties be seated when the majority party claims over two-thirds of the seats in either chamber.  Although this method is helpful – and indeed more advanced in terms of ensuring opposition representation than any other used in the US – it is still deeply imperfect. Add-on members are elected by the following method, proscribed by the constitution:

In order to select additional members of the Legislative Assembly from a minority party in accordance with these provisions, its candidates at large who have not been elected shall be the first to be declared elected in the order of the votes that they have obtained, and thereafter its district candidates who; not having been elected, have obtained in their respective districts the highest proportion of the total number of votes cast as compared to the proportion of votes cast in favor of other candidates of the same party not elected to an equal office in the other districts.

In 2008, one list and two district candidates for the Popular Democrats were elected from each house under this provision. One unfortunate effect of this guarantee can be seen in the at-large results: every candidate from the major parties who stood was elected, without exception. This universal election rate must be gratifying for major parties and their candidates, but stifling for minor parties (who won nothing) and demoralizing to voters, whose choices barely affect outcomes. Another difficulty arises with the district candidates, though they ran to represent a specific geographic area, winners under the minority provision are considered at-large members. Thus they are in an odd position, elected to a position they did not run for and representing constituents who did not vote for them. Though Puerto Rico's attempts to ensure fair representation are ingenious – and go further than any other US jurisdiction -- they could be improved through the adoption of a fairer electoral system such as choice voting or instant runoff voting.  These methods would hew closer to democratic ideals by allowing voters to choose their own diversity, instead of mandating it though complex and inefficient constitutional provisions.