The four main presidential candidates are set to face off in their final TV debate Wednesday.

The debate comes a week before the election and two days before the start of early voting over two days.

The two-hour session will be hosted by the National Election Commission, the state election watchdog, and focus on social issues, such as welfare policies and the demographic crisis.

All four candidates -- Lee Jae-myung of the ruling Democratic Party, Yoon Suk-yeol of the main opposition People Power Party, Ahn Cheol-soo of the centrist People's Party and Sim Sang-jeung of the progressive Justice Party -- have cleared their public schedules on Wednesday to prepare for the debate.

Meanwhile, Kim Dong-yeon, a minor candidate of the New Wave Party, held a press conference to announce he was dropping out of the race to support Lee.

The two earlier reached an agreement to jointly pursue various political reforms, including revisions to the Constitution and electoral system.

Lee and Yoon, the two front-runners, have come under fire for their comments during the previous debate last Friday.

Lee said Ukrainian President Volodymyr Zelenskyy "provoked" Russia into invading his country by declaring plans to join NATO.

Yoon stopped short of categorically rejecting the possibility of Japanese troops entering the Korean Peninsula in the event of a contingency, saying it could happen if South Korea formed a trilateral military alliance with the United States and Japan but would not necessarily be the case.

Wednesday's debate will mark the first time Yoon and Ahn have met since merger talks broke down.

The two have been under pressure from conservatives to unify their candidacies in order to ensure an opposition victory over Lee.

Lee and Yoon have been neck and neck in the polls with around 40 percent support each.

In a Realmeter survey conducted Monday and Tuesday, Yoon earned 46.3 percent support against Lee's 43.1 percent.

In a poll conducted by Ace Research and Consulting Group on Sunday and Monday, Yoon led Lee 44.6 percent to 43.7 percent.

Both surveys had a margin of error of plus or minus 3.1 percentage points at a 95 percent confidence level.

These polls were among the last to be published before the election, as by law, polls conducted within six days of the election cannot be published until after voting closes. (Yonhap)

For more information regarding the survey results, go to the National Election Survey Deliberation Commission homepage.