President Park Geun-hye faces an impeachment vote in parliament on Friday over an influence peddling scandal that could lead to her becoming South Korea's first democratically elected leader to be removed from office in disgrace.
There have been mass rallies every Saturday for the past six weeks calling for Park to quit, and opinion polls show overwhelming public support for her impeachment.
Parliament is expected to vote in favour of impeachment, with support from some members of Park's conservative Saenuri Party, according to opposition parties but the Constitutional Court must decide whether to uphold the motion, a process that could take up to 180 days.
The parliamentary session for the vote was scheduled to begin at 3 p.m. (0600 GMT), with the secret balloting expected to take about one hour, according to media reports.
Park, 64, is accused of colluding with a friend and a former aide, both of whom have been indicted by prosecutors, to pressure big businesses to donate to two foundations set up to back her policy initiatives.
She has denied wrongdoing but apologised for carelessness in her ties with her friend, Choi Soon-sil.
Park said this week she would await the court's ruling, signalling that political crisis could drag on.
The daughter of a military ruler who led the country for 18 years before being assassinated by his disgruntled spy chief in 1979, Park is under intense pressure to step down immediately.
If Park did resign she would lose presidential immunity, and could be prosecuted for abuse of power and bribery, among other charges.
A poll released on Friday showed her approval rating stood at 5 percent, a slight improvement from a record low 4 per cent.
The survey by Gallup Korea - which is not affiliated with U.S.-based Gallup, Inc. - also showed 81 percent of respondents supported impeachment.
Parliament introduced the impeachment bill on Thursday and it must be voted on within 24 to 72 hours at the domed National Assembly building that sits on an island on the south side of the Han River.
If the motion passes, the Constitutional Court will determine whether parliament followed due process and whether there are sufficient grounds for impeachment, a process that will involve arguments from the two sides in public hearings.
Prime Minister Hwang Kyo-ahn, who holds what is largely a ceremonial role, would assume interim presidential powers while the court deliberates.
Hwang would take the helm at a time heightened tension with North Korea.
South Korea's economic outlook is worsening too, in part due to the internal political uncertainty, as well as worries about the potential impact of U.S. President-elect Donald Trump's policies on trade and foreign affairs.
The 9-member court is considered conservative in its makeup but some of its former judges have said the case against Park is strong and was likely to be approved.
The Bank of Korea will hold emergency meetings to review policy measures that may be taken against any fallout from the vote, a central bank official said.
SOLE PRECEDENT
In 2004, parliament impeached then-president Roh Moo-hyun, suspending his powers for 63 days while the court reviewed the decision, which it overturned.
The most-searched items on leading web portal Naver on Friday were related to what happened around Roh's impeachment.
The prime minister at the time, Goh Kun, said in a 2013 memoir that he had decided to stay "low key" while he held the reins of power.
"Even if his duty was suspended, President Roh was staying at the Blue House residence. There was no need to create unnecessary tension," Goh wrote.
The stakes are high for both sides. The leaders of the two main opposition parties said their 159 members would all resign if the impeachment motion failed, taking responsibility for their inability to follow through on the demands of the public.