Early exit polls in South Korea's parliamentary elections on Wednesday indicated that the ruling conservative party was unlikely to win an absolute majority for the first time in 16 years, broadcaster KBS reported.
For President Park Geun Hye and her Saenuri Party, which had been widely favoured to come out on top, their shrinking influence will make achieving the party's political aims, notably contested economic reforms, much more difficult before Park leaves office in 2018.
According to the broadcaster's calculations, the Saenuri Party is expected to take only 121 to 143 seats, putting it just slightly ahead of the largest opposition party, the Minjoo or Democratic Party of Korea (MPK), which will likely win 101 to 123 spots.
The newly formed liberal People's Party is expected to remain in third with 34 to 41 seats.
At stake in Wednesday's race are all 300 seats.
The parliamentary election, which takes place in a four-year cycle, is seen as an important test of the political atmosphere in Asia's fourth-largest economy ahead of presidential elections at the end of 2017.
A good election result can boost a party's votes for the presidency. South Korea's presidential system permits the head of state to govern even over an opposition majority in parliament.
Park, who remains in office until February 2018, cannot stand for re-election once her five-year term is up.