Philippine Senate elections

Map of the senatorial districts.

From 1916 to 1934, the country was divided into 12 senatorial districts. Eleven of these districts elected two senators each. In 1916, each district elected two senators (plurality-at-large): one was to serve a six-year term, the other a three-year term. On each election thereafter, one seat per district was up (first past the post). The senators from the 12th district were appointed by the American governor-general for no fixed term.[3]

In 1935, the electorate approved in a plebiscite a new constitution that abolished the Senate and instituted a unicameral National Assembly of the Philippines. The members of the Constitutional Convention originally wanted bicameralism but could not agree on how the senators shall be elected: via the senatorial districts or being nationally elected.[4]

The electorate In 1940 approved in a plebiscite amendments to the constitution that restored the bicameral Congress of the Philippines, including the Senate. Elections for the Senate were held on every second Monday of November of every odd-numbered year; however, the old senatorial districts were not used anymore; instead, the 24-member Senate was to be elected on a nationwide at-large basis.[4] As the first election in the new setup, the voters in the 1941 election voted for 24 senators. However, they were also given the option of writing the party's name on the ballot, wherein all of the candidates of the party would receive votes. With the 24 candidates with the most votes winning in the election, the ruling Nacionalista Party won all 24 seats in a landslide victory. The winners included Rafael Martinez, who replaced Norberto Romualdez, who died the day before the election; Martinez won because of voters who had selected the party, rather than specifying a particular candidate.[5]

Due to World War II, Congress was not able to convene until June 1945. President Sergio Osmeña called for special sessions to convene the 1st Congress of the Commonwealth of the Philippines until elections could be organized. Originally, to observe the staggered terms, the eight candidates with the most votes were to serve for eight years, the next eight for four years, and still the next eight for two years. However, several members had died and others were disqualified because they were charged with collaboration with the Japanese, so the Senate conducted a lottery to determine which senators would serve until 1946 and which would serve until 1947.[6] In the 1946 election, voters elected 16 senators; the first eight candidates with the highest number of votes were to serve until 1951, the next eight were to serve until 1949.[3]

The Senate chamber at the Old Congress building: Cipriano P. Primicias, Sr., far left, debates Quintín Paredes, far right. In the center are, from left to right, Justiniano Montano, Mariano Jesús Cuenco, Enrique B. Magalona, and Francisco Delgado. In the foreground is Edmundo Cea.

Electoral reform enacted in 1951 eliminated block voting, which had given voters the option of writing the party's name on the ballot. In a 1951 election, voters voted for eight senators for the first time and each voter had to write at most eight names for senator (writing the party's name would result in a spoiled vote). Noting that after the elimination of block voting, many people voted for a split ticket, political scientist David Wurfel has remarked that "The electoral reform of 1951 was thus one of the most important institutional changes in the postwar Philippines, making the life of the opposition easier."[5]

On September 23, 1972, President Ferdinand Marcos declared martial law and assumed legislative powers. In a 1973 plebiscite, the electorate approved a new constitution that abolished Congress and replaced it with a unicameral National Assembly, which would ultimately be the Batasang Pambansa (parliament).[3]

The GSIS building: The Senate session hall.

Marcos was overthrown as a result of the 1986 People Power Revolution. The new president, Corazon Aquino, appointed a Constitutional Commission to write a new constitution. The electorate approved the constitution in 1987, restoring the bicameral Congress. Instead of electing 8 senators every two years, the new constitution provided that 12 senators would be elected every three years. As part of the transitory provisions, the voters elected 24 senators in the 1987 election, to serve until 1992. In the 1992 election, the voters still voted for 24 candidates, but the first 12 candidates with the most votes were to serve until 1998, while the next 12 were to serve only until 1995. Thereafter, 12 candidates are elected every second Monday of May every third year since 1995.[7]

In this table, the "administration" ticket is the ticket supported by the sitting president. In 1992, Corazon Aquino who was nominally supporting the LDP, supported the presidential candidacy of Fidel V. Ramos of Lakas, making the "administration ticket" ambiguous.

^1 replaced by Koko Pimentel as a result of an election protest.