LDP spokesman Ramon Bagatsing said the remaining candidates of the 12-member slate would come from major opposition parties inclined to coalesce with the LDP.
The initial eight candidates included Senators Rodolfo Biazon and Teresa Aquino-Oreta and former Senators Juan Ponce Enrile, Miriam Defensor-Santiago and Francisco Tatad.
Bagatsing said Representatives Carlos Padilla and Ted Failon would be the House voice in the slate while Camarines Sur Gov. Luis Villafuerte "will be most likely" to represent the local government units.
Sen. Aquilino Pimentel Jr., of the PDP-Laban, would be a "valued member of the LDP team" if his party were to agree to join the LDP, he said in a statement.
Other politicians being eyed to complete the slate were North Cotabato Gov. Emmanuel Piñol, of Lakas, and Ilocos Norte Rep. Imee Marcos.
"While the ruling coalition is in the process of dismemberment, the political opposition is solid and cohesive," Bagatsing, a former Manila congressman, said.
Bagatsing claimed that surveys show that Biazon, Oreta, Enrile, Santiago, Pimentel and Tatad were "sure winners" in the coming senatorial elections. Padilla, Failon, Villafuerte, Marcos and Piñol were "strong candidates," he said.
"If senatorial elections were to be held today, the opposition candidates will be the runaway winners," he said.