Senate in the 17th Congress: Makeup and alliances

Metro Manila (CNN Philippines) — Shortly after polling precincts closed for the 2016 elections and unofficial tallies showed an apparent clear presidential winner, three political parties — one after the other — signed a coalition agreement with incoming president Rodrigo Duterte's Partido Demokratiko Pilipino-Lakas ng Bayan (PDP-Laban).

These were the Nacionalista Party (NP), Lakas-Christian Muslim Democrats (Lakas-CMD) and the Nationalist People's Coalition (NPC).

Related: PDP-Laban, Lakas-CMD sign 'coalition for change'

When the 17th Congress opens, the NP will have three members in the Senate -- Alan Peter Cayetano, Antonio Trillanes, and Cynthia Villar.

The NPC, which supported the presidential bid of Sen. Grace Poe, also has three members in the upper chamber — Tito Sotto, Win Gatchalian, and Loren Legarda.

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The shifting of alliances isn't surprising, according to political analyst Temario Rivera.

Rivera said on Friday (May 20) that party loyalty remained almost non-existent in Philippine politics.

Two reasons accounted for this: a weak party system and a very powerful presidency.

As for the next senate president, at least two names are being floated. 

These are PDP-Laban President Koko Pimentel and reelected senator Tito Sotto.

Sotto told CNN Philippines that 11 senators considered him an alternative candidate.

But Rivera believed Pimentel was the frontrunner for the senate presidency.

He added that the Liberal Party (LP) would be the single biggest minority, as most of the independent senators — Ping Lacson, Poe, Chiz Escudero, Migz Zubiri and Dick Gordon — would likely support Duterte.

There's a little more than a month away until the people see alliances take final shape in the Senate.

But Rivera said one thing remained sure — nothing would be permanent in politics.

CNN Philippines' Anna Estanislao contributed to this report.