The electoral system of the Islamic Republic of Pakistan is governed by its Constitution which was passed by the National Assembly on April 10, 1973 and modified up to the 28th of February, 2012.
Majlis-e-Shoora, the Parliament of Pakistan, is composed of the President and two Houses—the National Assembly and the Senate.
Article 41 of the Constitution provides that the President shall be the head of State and is elected by members of an electoral college which consists of members of both Houses of the Parliament and members of the Provincial Assemblies. Only a Muslim who is at least 45 years of age and is qualified to be a member of the National Assembly can be elected in the seat of the President. However, the elected cannot be a Member of Parliament or a Provincial Assembly; in the case that the elected is a member, his seat must be vacant upon entering office, which lasts for five years.
The National Assembly has 342 seats, which are allocated to each province, the Federal Administered Tribal Areas (FATA) and the Federal Capital, including seats for women and non-Muslim. Its electoral system is based on single-member territorial constituencies wherein its members are elected by direct vote through the first-past-the-post system. Seats for women and non-Muslim are filled through a separate electoral system—they are elected through an indirect proportional representation list system. Prior to the election, the lists of candidates for reserved seats are filed by the political parties to the Election Commission. When the general seats are settled, the seats for women are filled based on the total number of general seats secured by each political party from the Province concerned in the National Assembly while those of non-Muslims are based on the total number of general seats won by each political party in the National Assembly.
The Senate has 104 members, elected via the Electoral College. The Electoral College for Senate seats allocated for provinces consists of members of the Provincial Assembly. Their seats are filled through proportional representation on the basis of single transferable vote. The Electoral College for the FATA and Federal Capital seats is the members of the National Assembly from FAT and the entire National Assembly, respectively. Votes are separately cast for each category—General, Women, Technocrats and Minorities—on separate ballot papers with different colors (with the exception of FATA having only one category which is the General seats).
Article 106 rules that Provincial Assemblies consist of general seats and seats reserved for women and non-Muslims. The seats are filled based on single-member constituencies, elected directly by citizens. Reserved seats for women and non-Muslims are filled through the proportional representation list system based on the total number of general seats secured by each political party in the Provincial Assembly.
A by-election may be held when a seat in the National Assembly becomes vacant resulting from death, resignation or disqualification of a member and should be held within 60 days of the vacancy in the respective constituency. But if a seat becomes vacant within 120 days of the expiration of the term, a by-election is not held. If the vacant seat is that reserved for women or non-Muslims in the National or a Provincial Assembly, it is filled by the next person in order of preference from the list of the candidates submitted to the Election Commission of Pakistan for the most recent General Election by the party whose member vacated the seat. A by-election may also be held when a seat is vacated due to complication of candidates having won seats in more than one constituency and must, therefore, resign from other constituencies, leaving only one seat which he will occupy. This occurs because candidates are allowed to run simultaneously in multiple constituencies. Thus, several by-elections are held immediately after the General Elections.
Source:
Legal Framework for Senate Election. (n.d.). Retrieved from Pakvoter.org:
http://www.pakvoter.com/content/legal-framework-senate-election
Pakistan Factsheet: National Assembly. (n.d.). Retrieved from Pakvoter.org:
http://www.pakvoter.com/content/pakistan-factsheet-national-assembly
Senate Elections. (n.d.). Retrieved from Senate of Pakistan:
http://www.senate.gov.pk/en/essence.php?id=24&catid=4&subcatid=138&cattitle=About%20the%20Senate
The Constitution of the Islamic Republic of Pakistan