The 1998 election of members to the Senate of the Philippines was the 26th election to the Senate of the Philippines. It was held on Monday, May 11, 1998 to elect 12 of the 24 seats in the Senate. The two main competing coalitions in the senatorial election were Lakas—National Union of Christian Democrats—United Muslim Democrats of the Philippines and the Laban ng Makabayang Masang Pilipino umbrella coalition composed of Laban ng Demokratikong Pilipino, Pwersa ng Masang Pilipino, Nationalist People's Coalition, and Partido Demokratiko Pilipino—Lakas ng Bayan. The two coalitions split the 12 contested seats 7–5 in favor of LAMMP.
The two major presidential candidates, House Speaker Jose C. de Venecia Jr. of Lakas—NUCD—UMDP and Vice President Joseph E. Estrada of LAMMP presented full 12-person senatorial slates.
Former National Defense Secretary Renato de Villa's Partido ng Demokratikong Reporma, Santiago Dumlao's Kilusan para sa Pambansang Pagpapanibago, and Manila Mayor Alfredo Lim's Liberal Party also presented senatorial slates.
Oliver Lozano was the sole independent not included in senatorial slates who was allowed to run.
These all won in the 1995 election, and if lost, would have still returned to finish their six-year Senate term.
Arroyo's victory in the vice presidential election meant that she would vacate her Senate seat by June 30, 1998.
The Laban ng Makabayang Masang Pilipino (LAMMP) won seven seats, while the Lakas-NUCD won five.
Three incumbents, all from LAMMP, successfully defended their seats: Blas Ople, Ramon Revilla Sr., and Tito Sotto.
There are five neophyte senators: Rene Cayetano, Loren Legarda, and Robert Barbers of Lakas, and Robert Jaworski and Tessie Aquino-Oreta of LAMMP.
Returning senators are Rodolfo Biazon, John Henry Osmeña, and Aquilino Pimentel Jr. of LAMMP, and Teofisto Guingona, Jr. of Lakas.
Freddie Webb was the sole incumbent defeated.
The election of Gloria Macapagal Arroyo as Vice President of the Philippines in a concurrent election meant that her Senate seat was vacant until June 30, 2001.
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