South Korea's political turmoil means the next presidential campaign has started, at least unofficially. The election is scheduled for December but if suspended President Park Geun-hye is dismissed it will happen sooner -- and candidates are preparing.
Moon Jae-in is a former leader of the largest opposition party and one of the most strident critics of Park Geun-hye, who narrowly defeated him in the last election.
"The construction of a new South Korea is possible if it's based on strong security. I cannot let anyone who's suspected of corruption or who aren't competent lead the country," Moon said.
In his early years, he fought against poverty, and the military government led by Park's father. Moon was arrested in college but went on to become a human rights lawyer.
He worked with former President Roh Moo-hyun at a law firm, as well as when he led the country. Some supporters hope Moon will more effectively deal with North Korea.
"The Park administration only imposed sanctions on the North," says one of his supporters. "I expect that Moon may show a more rational solution that's neither a one-way dialogue nor sanctions."
Then there's the international figure Ban Ki-moon, who has just finished 2 terms as secretary-general of the UN.
"I intend to unite this divided country and make it a first-rate nation again," Ban said.
He flew back to Seoul on Thursday and then took a train to his home, saying he wanted to act like an ordinary citizen.
Ban's father went bankrupt and he grew up in poverty, but he succeeded in school and went on to build a career at the Foreign Ministry. He served as foreign minister under President Roh, a liberal.
Ban has not yet announced which party he will run for.
"I expect him to contribute to create a new country based on his experience," says one of his supporters.
Lee Jae-myung is the mayor of a Seoul suburb who is quickly becoming popular, especially with young people.
"We should promote a just society, based on fairness, equality and peace, and guarantee human rights and social welfare," Lee said.
He speaks frankly and is called the "Donald Trump of South Korea."
"Lee tries to communicate with us through Twitter. It's really different from the current president," says one of his supporters.
And Ahn Cheol-soo graduated from medical school, but became the CEO of an IT company. There, he distributed security software for free and became known as South Korea's Bill Gates.
"I made up my mind to bring change to this country, because people are so eager for it," Ahn said.
He also ran for president in 2012 but withdrew, saying he wanted to help Moon Jae-in beat out Park.
NHK World's Kim Chan-ju and Hiroki Yajima join Mistuko Nishikawa in the studio from Seoul.
Nishikawa: Chan-ju, the race isn't officially underway just yet but how are things shaping up so far?
Kim: Well, because of the uncertainties surrounding the election, like when it will happen, none of these men have actually made it clear they will run for certain. But the latest poll shows Moon Jae-in is in the lead with 31 percent support. Ban Ki-moon is next at 20 percent, Lee Jae-myung at 12 percent, and Ahn Cheol-soo at 7 percent.
The poll included 4 other possible candidates that all have less support. Th prime minister and acting president, Hwang Kyo-ahn, is one of them, as are a governor and a current and a former lawmaker.
A poll by 2 major South Korean media organizations showed similar results, but of course it's still very early and things could change significantly once the election is officially called.
Nishikawa: And let's bring in our correspondent Hiroki Yajima. So Hiroki, how do people's political leanings play into those candidate support numbers?
Yajima: The past decade has seen 2 consecutive conservative administrations. Before that, it was a decade of liberal governments. We know people are very angry over the current scandal and then there's general dissatisfaction that comes when a party spends a good amount of time in power. So it's not hard to imagine the vote shifting back to a liberal candidate or a third non-traditional option.
Keep in mind, in South Korea's voting system, voters cast ballots directly for their desired candidate. So, while political leanings are important, so is a candidate's popularity.