South Korea's presidential candidates formally began campaigning on Tuesday what local media say is set to be the tightest race in 20 years between its two main parties. 

The candidates can now rally on streets and run ad campaigns in a final appeal to voters ahead of the election on March 9.

Polls say voters are looking for a president who can clean up polarized politics and corruption, and tackle the runaway housing prices and deepening inequality.

14 candidates have signed up since official registration opened on Sunday, with Lee Jae-myung, the flag-bearer of the ruling Democratic Party, facing off Yoon Suk-yeol from the conservative main opposition People Power Party.

Dubbed the "unlikeable election" due to high disapproval ratings and smear campaigns waged by both sides, Lee and Yoon are neck and neck in polls, although Yoon has maintained a slight lead in recent weeks.

A former governor of Gyeonggi province, Lee shot to prominence through his aggressive handling of the COVID-19 pandemic and his advocacy of universal basic income.

Yoon is a political novice, but has gained popularity thanks to his image as a staunch prosecutor-general who steered high-profile investigations into corruption scandals engulfing aides to former President Park Geun-hye and current President Moon Jae-in.

But growing frustration over mainstream politics and controversy involving both candidates' families have been a fillip for Ahn Cheol-soo, a renowned software mogul and doctor who is a minor opposition contender.

Ahn formally offered (on Sunday) to merge campaigns with Yoon, saying it would expedite a "overwhelming victory" and national unity. Yoon said he would give the proposal "positive consideration.”

(With input from Reuters)