Philippine senatorial elections

Elections to the Senate of the Philippines is done via plurality-at-large voting; a voter can vote for up to twelve candidates, with the twelve candidates with the highest number of votes being elected. The 24-member Senate uses staggered elections, with only one-half of its members up for election at any given time, except for special elections, which are always held concurrently with regularly scheduled elections.

With the advent of the nominal multi-party system in 1987, political parties have been able to muster enough candidates to fill their 12-person ticket. This means they have to join coalitions or alliances in order to present a full slate. If a slate is still not complete, guest candidates may be invited, even from rival slates. A guest candidate may not be compelled to join the campaign rallies of the slate that invited him/her. A party may even not include their entire ticket to a coalition slate, or assign their candidates to competing slates. A candidate may defect from one slate to another or be unaffiliated with any slate while the campaign is ongoing. The Commission on Elections uses the names of the political parties on the ballot.

In Third Republic elections under the nominal two-party system, the Liberal Party and the Nacionalista Party often presented complete 8-person tickets; a party may even exceed the 8-person slate due to perceived popularity.

Once elected, the parties involved in the different slates may form alliances with one another totally different from the alliances prior to the election.

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.

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