Elections in Puerto Rico are guaranteed by Article VI of the Constitution of Puerto Rico and the Electoral Code of Puerto Rico for the 21st Century Act. All processes are overseen and managed in whole by the Puerto Rico State Elections Commission; an autonomous agency of the executive branch of the government of Puerto Rico.
There are three types of electoral processes that occur in Puerto Rico:general elections which are held every four years on the first Tuesday after the first Monday of November, and where the people of Puerto Rico elect their:Governor,
members of the Legislative Assembly, including both the:
House of Representatives,
referendums which occur after a law has been enacted calling for a referendum, and
special elections which occur when a vacancy occurs on a post or for other similar matters.
Citizens of the United States residing in Puerto Rico can not vote for their head of state, the President of the United States, due to the political status of Puerto Rico.
The latest general election was held on November 6, 2012 which resulted in the election of Alejandro Garcia Padilla as governor, Pedro Pierluisi as Resident Commissioner, the member elections of the 17th Legislative Assembly of Puerto Rico (including the 25th Senate of Puerto Rico and the 29th House of Representatives of Puerto Rico), and the election of the 2013 mayors and their respective municipal assemblies.
The latest referendum was held on the same date and resulted in Puerto Ricans expressing themselves against maintaining the current political status of Puerto Rico and preferring statehood should Puerto Rico's political status change.
Only American citizens (including Puerto Ricans) that meet all the following requirements may vote:must legally reside in Puerto Rico,
must be at least 18 years old by the date of the election,
must have been qualified by the Puerto Rico State Commission on Elections before the election or on the very same day of the election after he presents himself to his nearest place of voting and shows proper documentation, and
must have not been declared mentally incapacitated by court.
Citizens cast their votes in colleges (Spanish: colegios) which are simply usually the nearest public school to where the voter declared as residence. Citizens are required by law to vote in secret, unless they have a physical impairment that does not allow them to. Those unable to travel to colleges due to medical impairments may vote at their place of residence (homes, elder homes, etc.) or wherever they are convalescing (hospitals, clinics, etc.). In both of these extraordinary cases, officials from the Puerto Rico State Commission on Elections will provide aid so that the citizens can cast their vote—either by using verbal or non-verbal communication—with members from the different political parties required to observe the process in order to ensure accuracy, fairness, transparency, order, and legitimacy.
Ballots are published in both English and Spanish regardless of whether English is an official language or not.
Puerto Rico elects on state level a governor and a legislature. The island's governor is elected for a four-year term by the people.
The Legislative Assembly (Asamblea Legislativa in Spanish) has two chambers: the Chamber of Representatives (Cámara de Representantes in Spanish) and the Senate (Senado in Spanish) which is elected for a four-year term concurrently with the governor.
Although Puerto Rico has a three-party system, the two major parties are those that wish to maintain ties with the US government dominate; the third party, favoring independence, obtains only a small percentage of the votes.
In the 2008 elections, a fourth party participated, the Puertorriqueños por Puerto Rico (PPR). In 2012 six parties are expected to participate, the same four as in 2008 and two new ones: Partido del Pueblo Trabajador (PPT), and Movimiento Union Soberanista (MUS).
The Senate of Puerto Rico currently has 27 members, including:16 members elected from 8 two-seat electoral districts through plurality at large (each Senate district comprises 5 House districts)
11 at-large members
The House of Representatives of Puerto Rico currently has 51 members composed of:40 elected in single-seat electoral districts using first-past-the-post
11 at-large members
In each house, 11 at-large members are elected from an island-wide district based on single non-transferable vote. To avoid vote splitting, the two major parties will typically nominate only 6 members and smaller parties typically only nominate one. Additionally, parties may choose the ballot order of its candidates in different districts, in an attempt to signal to voters the preferred method of voting. However, each voter is free to choose any candidate.
As the electoral system is majoritarian, the section 7 of Article III of the Puerto Rican constitution s:Constitution of the Commonwealth of Puerto Rico allows for additional members to be added to either chamber to enhance the opposition party's representation. Members of the opposition will be added to provide a minimum of 17 and 9 members of the House and Senate, respectively (one third of the original size). In the last election, 2 and 3 members were added to the House and Senate, respectively.
When the majority party polls less than two-thirds of the vote for Governor of Puerto Rico, minority seats in the Senate or the House are distributed using a variant of the Hare quota largest remainder method according to the minority parties' share of the vote for governor, subject to a 3% threshold. 
A slightly different procedure is provided for in the event the majority party wins more than two-thirds of the vote for governor, which limits each minority party to a number of seats not in excess of its proportionate share of its vote for governor (excluding rounding differences).
Additional seats assigned to a minority party first go to defeated at-large candidates with the largest vote totals, and then, if necessary, to district candidates with the largest proportion of the vote who have not been elected (sometimes called the "best loser" system).