(EDITOR'S NOTE: This is a developing story that will be refreshed with updates.)

MANILA (UPDATED) - Pampanga Rep. Gloria Arroyo was on the verge of assuming the House of Representatives leadership on Monday, in a political power play with Speaker Pantaleon Alvarez that delayed President Rodrigo Duterte's State of the Nation Address (SONA).

At one point, Arroyo took her oath of office at the Batasang Pambansa rostrum in an apparent unofficial session, while Alvarez was waiting to welcome Duterte in another part of the lower House.

At least 161 congressmen signed a manifesto that sought to name Arroyo as speaker, according to Deputy Speaker Rolando Andaya. But before Duterte delivered his SONA, it was Alvarez who sat on the speaker's chair.

“The House of Representatives, and the Nation, will benefit from the experience, competence, sobriety, steady, and unifying leadership of former president and Rep. Gloria Macapagal Arroyo as Speaker,” a copy of the manifesto circulated among reporters read.

“As many critical issues involving the future structure and framework of our government will need to be discussed very soon, a credible and competent House leadership will be needed to guide and steer the national debate towards a resolution of these pending issues,” the document read.

Arroyo, who is on her last term as congresswoman, will be the first former president to lead the House.

Alvarez’s allies allegedly tried to stop his removal as Speaker by abruptly adjourning the opening session, which also led to the House’s failure to ratify the Bangsamoro Organic Law before the President’s third SONA.

“Hindi naman sinet aside [ang BOL] but it was overtaken by intramurals within the administration coalition,” Akbayan Party-list Rep. Tom Villarin told reporters.

Alvarez's removal came after he quarreled with his erstwhile political patron, Davao del Norte 2nd District Representative Antonio Floirendo Jr., one of the biggest donors in Duterte's 2016 presidential campaign.

Alvarez also had a public spat with President Rodrigo Duterte's daughter, Davao City Mayor Sara Duterte-Carpio.

Duterte-Carpio had slammed Alvarez for allegedly calling her a part of the opposition when she formed a separate regional political party. Alvarez denied this, saying the mayor's new party was a "non-issue."

Arroyo was released from detention in June 2016 after the Supreme Court nullified evidence lodged against her in a plunder case.