2019 Philippine House of Representatives elections

The Philippines uses parallel voting for its lower house elections. There are currently 297 seats in the House; 238 of these are district representatives, and 59 are party-list representatives. Philippine law mandates that there should be one party-list representative for every four district representatives. District representatives are elected under the plurality voting system from single-member districts. Party-list representatives are elected via the nationwide vote with a 2% "soft" election threshold, with a 3-seat cap. The party in the party-list election with the most votes usually wins three seats, the other parties with more than 2% of the vote two seats, and the parties with less than 2% of the vote winning a seat each if the 20% quota is not met.

Campaigning for elections from congressional districts seats are decidedly local; the candidates are most likely a part of an election slate that includes candidates for other positions in the locality, and slates may comprise different parties. The political parties contesting the election make no attempt to create a national campaign.

Party-list campaigning, on the other hand, is done on a national scale. Parties usually attempt to appeal to a specific demographic. Polling is usually conducted for the party-list election, while pollsters may release polls on specific district races. In district elections, pollsters do not attempt to make forecasts on how many votes a party would achieve, nor the number of seats a party would win; they do attempt to do that in party-list elections, though.

Reapportioning the number of seats is done via national reapportionment after the release of every census or via piecemeal redistricting for every province or city. National reapportionment has not happened since the 1987 Constitution took effect, and aside from piecemeal redistricting, the apportionment was based on the ordinance from the constitution, which was in turn based from the 1980 census.

In total, seven new district seats were created. Two were in Isabela, where the entire province was redistricted from four districts to six, and one each in Cavite, where the sixth and seventh districts were redistricted into three, Aklan and Southern Leyte, which were split into two districts, Laguna, where Calamba was separated from the second district and South Cotabato, where General Santos was separated from the first district.

As there are now 245 districts; therefore, there are 61 party-list seats (at least 20% of the total), an increase from 59. The 18th Congress shall then have 306 representatives. However, as preparations were already on its way when the laws for the creation of General Santos and Southern Leyte districts were made, the commission decided to delay elections for the four seats involved to October 2019; the ballots for those districts showed their previous conflagrations as if it were not redistricted yet. A lawsuit was then decided by the Supreme Court prior to rescheduled elections, ordering the commission to declare the winner of the election in South Cotabato's 1st district. Upon doing so, the commission then declared the winner of the unified Southern Leyte district as well. The first elections for these two districts shall be on 2022, at the next general election. This left the number of districts to 243, with still 61 party-list seats.

These are the marginal seats that had a winning margin of 5% or less, in ascending order.