South Koreans voted Wednesday to elect the education chief of Seoul and four local government heads, with the result expected to serve as a litmus test of public sentiment since the April general elections.Up for grabs in Wednesday's by-elections are five local administrative seats -- the superintendent of the Seoul Metropolitan Office of Education, as well as the heads of Busan's Geumjeong District, Incheon's Ganghwa County, and the Yeonggwang and Gokseong counties in South Jeolla Province.Voting kicked off at 6 a.m. and is to run until 8 p.m. at 2,404 polling centers nationwide, according to the National Election Commission (NEC). Among the 8.64 million eligible voters, 775,971 already cast their ballots during the two-day early voting last week.Turnout of the advance voting came to 8.98 percent, the NEC said.Observers say the election could put to test the leadership of the ruling People Power Party (PPP) and the main opposition Democratic Party chiefs, Han Dong-hoon and Lee Jae-myung, respectively , who are considered the next presidential candidates.The outcome of the election could also shape the second half of President Yoon Suk Yeol's five-year term, as the opposition intensifies its political offensive against the PPP and the president, with some even raising the possibility of Yoon's impeachment.Source: Yonhap News Agency