South Korea's presidential candidates formally began campaigning Tuesday in what is set to be the tightest race in 20 years between the country's two main parties, dominated by scandals that have allowed a third challenger to potentially play the role of kingmaker.

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 that have dogged Asia's fourth-largest economy.

Curbing North Korea's weapons tests and resuming talks would be a plus, but even a record month of missile testing by Pyongyang in January hasn't made foreign policy a key issue for the March 9 vote in South Korea.