Hugpong ng Pagbabago won overwhelmingly, while the main opposition coalition, Otso Diretso, was not able to win any seat in the Senate.

Senate elections in the Philippines are conducted via the plurality-at-large voting system, where the entire country is one at-large "district".

While the Philippines is a multi-party system, parties tend to group themselves into two major coalitions in midterm elections (e.g. Lakas-Laban vs NPC in 1995; PPC vs Puwersa ng Masa in 2001).

Winning candidates are proclaimed by the Commission on Elections (COMELEC), sitting as the National Board of Canvassers.

[6] In October 2017, the Partido Demokratiko Pilipino-Lakas ng Bayan (PDP–Laban) was only considering to form a coalition with the Nacionalista Party for the 2019 senatorial elections.

[7] In November 2017, PDP–Laban reportedly released a "partial list" of their senatorial slate for the 2019 edition consisting of six people.

It included himself and the five other senators that were members of the majority bloc, several administration officials, representatives, and private citizens.

Pimentel divided the names into three groups: members of PDP–Laban, outsiders, and the incumbent senators of the majority bloc.

[18] Leni Robredo announced that she accepted the role of opposition leader in the election, and they released the line-up by mid-September.

The line up may include former Chief Justice Maria Lourdes Sereno, who was removed from office by a quo warranto petition.

The list included incumbent senator Paolo Benigno "Bam" Aquino IV, Magdalo representative Gary Alejano, former Department of Interior and Local Government secretary Manuel "Mar" Roxas II, former chief justice Maria Lourdes Sereno, former Quezon representative Lorenzo "Erin" Tañada III, lawyer Jose Manuel "Chel" Diokno, former Bangsamoro Transition Committee member Samira Gutoc, former Solicitor General Florin Hilbay, former Akbayan representative Ibarra "Barry" Gutierrez III, actor Dingdong Dantes, former presidential spokesman Edwin Lacierda, writer Manuel Luis "Manolo" Quezon III, activist Leah Navarro, actress Agot Isidro, musician Jim Paredes, election lawyer Romulo Macalintal, former Social Welfare secretary Corazon "Dinky" Soliman, and ex-chief justice Hilario Davide Jr.[21] By October 2018, before the 2019 general elections, the Liberal Party formed the Otso Diretso (transl.

[23] As part of the Liberal Party's efforts to instill this new political culture, it launched Project Makining in October 2018, a modern, nationwide listening campaign driven by volunteers.

Senate Majority Leader Tito Sotto said Cojuangco was reportedly unsatisfied with how the party was being run, as leadership cannot agree on what direction to take.

Sotto also said that Bam Aquino, the only non-term limited incumbent from the minority bloc, was also invited to run in their slate.

Ejercito said this was to avoid his running together with his half-brother Jinggoy Estrada, under the Pwersa ng Masang Pilipino.

[33] On October 17, 2018, the party nominated three senatorial candidates for the 2019 midterm elections, namely Maria Socorro Manahan, Elmer Francisco, and Diosdado Padilla.

[34] A new political party, led by Consultative Committee on Constitutional Amendments member Ding Generoso fielded nine candidates in this mid-term election.

Alan Peter Cayetano (Nacionalista), who was on his second consecutive term, resigned from the Senate in order to become Secretary of Foreign Affairs on May 18, 2017.

Cayetano resigned as foreign affairs secretary on October 17, 2018, and filed his candidacy as House representative from Pateros and Taguig's 1st district.

Opinion polling, locally known as "surveys" in the Philippines, is conducted by Social Weather Stations (SWS), Pulse Asia and other pollsters.

Notes: On February 28, 2019, Otso Diretso candidates Gary Alejano, Samira Gutoc, Florin Hilbay, and Romulo Macalintal wrote a letter to the Commission on Elections (COMELEC), requesting to facilitate a debate with administration-supported party Hugpong ng Pagbabago.

[67] Prior to this, on February 25, the day of the 33rd anniversary of People Power Revolution, Otso Diretso had challenged the Hugpong ng Pagbabago candidates for public debate but none of them showed up in the event.

[73] Candidates campaigning from detention were previously allowed; Senator Antonio Trillanes ran and won in 2007 despite being jailed for taking part in the Oakwood mutiny.

Trillanes was ultimately convicted of participating in a coup d'etat after winning, but accepted the amnesty passed by Congress that was proposed by President Benigno Aquino III.

[74] While convicts are not allowed to run anymore unless pardoned or accepting an amnesty, these people had pending cases as of yet and were innocent until proven guilty.

[75] The House of Representatives, through Speaker Pantaleon Alvarez began its own hearings on constitutional change without the participation of the Senate.

Five incumbents won reelection: Cynthia Villar, Sonny Angara and Koko Pimentel of HNP, Nancy Binay from UNA, and independent Grace Poe.

Four neophytes won election: Bong Go, Ronald dela Rosa, Imee Marcos and Francis Tolentino, all from HNP.

Incumbents JV Ejercito of HNP and Bam Aquino of Otso Diretso did not successfully defend their seats.