Exit polls projected South Korea's ruling party was poised for a stinging blow Thursday as Seoul residents cast their votes for a new mayor, after the previous one took his own life following allegations of sexual abuse.
With around a fifth of South Korea's population living in Seoul, the vote held Wednesday is seen as a significant barometer of public opinion ahead of a presidential election next year.
The Democrats had picked a woman candidate to defend late mayor Park Won-soon's seat, but several of its top figures have lined up to defend him.
Female MPs have also privately denigrated Park's accuser, in what campaigners say shows how low a priority the progressive party of President Moon Jae-in -- who has called himself a feminist -- puts on women's rights.
Democrat candidate Park Young-sun, 61, a former journalist and four-term parliamentarian who has pushed for a 50 percent female legislature, had a mountain to climb as the polls opened.
The latest surveys from last week showed her around 20 points behind Oh Se-hoon of the conservative opposition People Power Party -- and exit polls early Thursday showed her set for what Yonhap news agency described as a "crushing defeat."
A similar by-election was also being held in the country's second city Busan, after its Democratic mayor was also accused of harassment and resigned, with the opposition on track for victory there also, according to exit polls reported by Yonhap.
Following Park's death in July, when he left a hand-written apology on his desk, Seoul's Democrat-controlled city administration held an official five-day mourning ceremony.
But in January, the National Human Rights Commission confirmed he had committed sexual misconduct, and his victim told reporters last month: "If the (next) mayor is elected from the party that hurt me, I fear that I will not be able to return" to normal life.
Party figures who have defended Park include Lim Jong-seok, Moon's former chief of staff.
Kwon Soo-hyun, president of Korea Women's Political Solidarity, told AFP: "These people have absolutely no interest when it comes to gender issues and women's rights."
The capital's soaring property prices have also been a key issue in the election, with many young citizens despairing of ever being able to afford a home of their own.