Choi Soon-sil (C), who is involved in a political scandal, reacts as she is surrounded by the media upon her arrival at a prosecutor's office in Seoul, South Korea, October 31, 2016. [Photo/Agencies]

SEOUL - A political scandal surrounding a longtime confidante of President Park Geun-hye derailed South Korea, heralding a big upheaval in the political landscape and in the dynamics of presidential election scheduled for next December.

Choi Soon-sil, who is known to have called President Park "sister" thanks to their seemingly indestructible friendship for decades, is now being placed by prosecutors under an emergency detention on Tuesday for alleged charges of intervening in state affairs and privatizing two non-profit foundations.

The 60-year-old woman is suspected of having edited the most important presidential speeches, including the one made in Dresden, Germany, in 2014 that laid out a vision for reunification with the Democratic People's Republic of Korea (DPRK).

Alleged wrongdoings committed by Choi involve her interference with the appointments of ministers, the shutdown of the inter-Korean factory park in Kaesong, the privatization of two non-profit foundations and pressures on a prestigious university to get her daughter granted special treatment.

President Park apologized to the public on Tuesday, acknowledging she had received personal advice from Choi on speeches and other public relations issues during the 2012 presidential election campaign and during her initial presidency on which Park didn't elaborate.

Even a day hasn't passed without new allegations on Choi's past irregularities. Student unions and professor groups in universities as well as civic group activists have rallied and held press conference nationwide to protest against President Park and her confidante suspected of peddling influence and pulling strings behind the scenes.

ALTERING POWER STRUCTURE

As tens of thousands of outraged protesters took to the streets in capital Seoul and major cities nationwide on Saturday night, President Park overhauled her secretariat on Sunday by accepting resignations of her key advisors.

Among the dismissed staff were three presidential secretaries, described as three "knobs of a door" that leads directly into the president. They had worked as Park's staff since she went into politics in 1998 as an elected lawmaker of the Grand National Party, predecessor of the current ruling Saenuri Party.

One of the three secretaries is suspected of bringing the copies of confidential presidential reports, including Park's schedule for overseas trip and secret military contacts with the DPRK under former President Lee Myung-bak, daily to Choi for review.

Also on the dismissal list were senior presidential advisor on policy coordination, who is accused of pressuring conglomerates into donating tens of millions of U.S. dollars to the Choi-controlled foundations, as well as senior presidential secretary for civil affairs in charge of overseeing prosecutors, police and spy agency.

The presidential chief of staff and the press secretary for President Park stepped down, along with senior advisor for political affairs who is tasked with communicating with political parties.

Choi Soon-sil, who is suspected of standing at the pinnacle of the power structure next to President Park, unexpectedly returned to Seoul on Sunday and appeared in prosecutors' office on Monday before being placed under an emergency arrest. Prosecutors requested a warrant to formally detain her.

The senior presidential advisor on policy coordination was summoned by prosecutors for questioning on Wednesday, and behind-the-doors aides to Choi with no official position and security clearance have been, or would be, grilled, in the prosecutors' office.

Power vacuum, caused by the resignations en masse and Choi's arrest, was first filled by two new secretaries. Park named new senior advisor for civil affairs and senior press secretary.

The relatively-rapid staff alteration for President Park is being led by former presidential chief of staff Kim Ki-choon and former deputy minister for economic affairs Choi Kyung-hwan, according to Chosun Ilbo newspaper citing a ruling party official.

Kim and Choi reportedly had a close relationship with Choi Jae-kyung, the new civil-affairs advisor for President Park. He is a former prosecutor famous for acquitting former President Lee Myung-bak of a charge of being involved in manipulating stock prices during the 2007 presidential primary of then ruling party.

DYNAMICS IN PRESIDENTIAL ELECTION

Outlook for next year's presidential election got blurred further as Saenuri Party lawmakers are raising different voices according to political interests. The non-President Park faction within the ruling party, composed of scores of lawmakers, has called on all of the party leadership to step down to take responsibility for the political crisis.

Five potential presidential hopefuls of the governing party, including former Saenuri chairman Kim Moo-sung, gathered on Tuesday to demand the resignation of the party leadership that was launched just around three months ago.

Kim, who led President Park's team for presidential election campaign in 2012 but is now categorized as a non-Park faction figure, said last Thursday that everyone did know Choi Soon-sil was close to Park when she was a presidential candidate in 2012. He said it was a lie to say that pro-Park figures didn't know the existence of Choi.

Expectations got high for forming a so-called "third playground", a claim that neutral political figures from both ruling and opposition parties gather in a third place for the 2017 presidential election. Possibility remains for part of Saenuri members to bolt from the embattled party and join the third bloc.

Traditional supporters for President Park are turning their backs rapidly. Park's approval rating dropped to a single-digit number for the first time during her four years in power. Most noticeable is an alienation of those in their 60s or above living in southeastern South Korea.

According to a Naeil Shinmun newspaper survey conducted on Oct. 31, Park's approval rating fell to 9.2 percent, down 25.0 percentage points from the previous month. Support for Park in the North Gyeongsang province tumbled from 44.3 percent to 8.8 percent.

Over 80 percent of respondents said the presidential personnel reshuffle will not contain public uproar, while about two-thirds of respondents agreed on the resignation of President Park.

Doubts remain about prosecutors' investigation into the Choi Soon-sil scandal as she was arrested belatedly. Many South Koreans still believe that time was enough for Choi to destroy evidence given that months have passed since allegations surrounding her surfaced in media reports.

Prosecutors raided the presidential office twice over the weekend, but they failed to enter inside the office for what the Blue House claimed was a possible leakage of classified documents. Instead, seven boxes of materials were voluntarily submitted to the prosecution.

When investigators stormed offices of the two foundations presumably controlled by Choi, the offices were almost empty, TV footage showed. All of computers in the K-Sports foundation were reportedly replaced, while email accounts of the employees were closed.