THE original purpose of the party-list system is as a form of affirmative action for smaller parties that may not be able to compete and win seats in legislative district elections. As designed, a party can obtain legislative seats not just by winning in district elections, but in proportion to the total votes they obtain nationally.

The usual manner this is implemented is that a voter casts two votes during election: one for the district representative and another for a political party. The legislature is thus composed of district representatives and of those who are elected in the party-list elections.