South Korean lawmakers are due to convene again over whether to impeach the president, Yoon Suk Yeol, for his failed martial law bid.

A week after the first attempt to remove Yoon foundered, the National Assembly is expected to vote at about 4pm local time on Saturday on whether to impeach him for “insurrectionary acts undermining the constitutional order”.

Two hundred votes are needed for the impeachment to pass, meaning opposition lawmakers must convince eight parliamentarians from Yoon’s conservative People Power party (PPP) to switch sides. As of Friday, seven ruling party lawmakers had pledged to support impeachment – leaving the vote up in the air.

Thousands of South Koreans have taken to the streets of Seoul to demand Yoon’s resignation and jailing after his short-lived martial law declaration sent soldiers and helicopters to parliament. Lawmakers quickly responded, breaking the military cordon and assembling in parliament to vote down the declaration.

Rallies supporting impeachment are expected to gather near the parliament about midday on Saturday. Organisers have promised to distribute food and banners to the protesters to lift their spirits in the freezing December temperatures. K-pop singer Yuri of the band Girls’ Generation – whose song Into the New World has become a protest anthem – said she had prepaid for food for fans that attended the rally. “Stay safe and take care of your health!” she said online.

Yoon has vowed to fight “until the very last minute” and doubled down on unsubstantiated claims the opposition is in league with South Korea’s communist foes.

The opposition Democratic party leader, Lee Jae-myung, has implored ruling PPP lawmakers to side with the “people wailing out in the freezing streets”. Two PPP lawmakers supported the motion in last week’s vote.

“History will remember and record your choice,” Lee said.

Kim Min-seok, an opposition lawmaker, said on Friday that he was “99%” sure the impeachment motion would pass.

Should it be approved, Yoon would be suspended from office while South Korea’s constitutional court deliberates. The prime minister, Han Duck-soo, would step in as the interim president. The court would then have 180 days to rule on Yoon’s future.

If it backs his removal, Yoon would become the second president in South Korean history to be successfully impeached.

There is precedent for the court to block impeachment: in 2004, the then-president Roh Moo-hyun was removed by parliament for alleged election law violations and incompetence, but the constitutional court later reinstated him.

The court also currently only has six judges, meaning its decision would need to be unanimous.

Should the vote fail, Yoon can still face “legal responsibility” for the martial law bid, Kim Hyun-jung, a researcher at the Korea University Institute of Law, said.

“This is clearly an act of insurrection,” she said. “Even if the impeachment motion does not pass, the president’s legal responsibilities under the criminal code … cannot be avoided.”

Yoon has remained unapologetic and defiant as the fallout from his disastrous martial law declaration has deepened and an investigation into his inner circle has widened.

On Friday, prosecutors said they had arrested a military commander who headed the capital defence command.

Arrest warrants were also issued by the Seoul central district court for the national police chief and the head of the city’s police, citing the “risk of destruction of evidence”.

Yoon’s approval rating – never very high – had plummeted to 11%, according to a Gallup Korea poll released on Friday. The same poll showed 75% supported his impeachment.

Protesters calling for his ouster for more than a week run the gamut of South Korean society: from K-pop fans waving glowsticks to retirees and blue-collar workers.

“Impeachment is a must and we must fight relentlessly,” said Kim Sung-tae, a 52-year-old worker at a car parts manufacturer. “We’re fighting for the restoration of democracy.”

Teacher Kim Hwan-ii agreed. “I’m so angry that we all have to pay the price for electing this president.”

With Agence France-Presse