While both have signaled a desire for greater engagement with Pyongyang, Park's approach is far more cautious than Moon's promise to resume aid without preconditions and seek an early summit with DPRK leader Kim Jong-un.

In her final national pitch at a televised news conference on Tuesday, the never-married Park promised a strong, maternal style of leadership that would steer the ROK through the challenges of the global economic crisis.

"I have no family to take care of, and no children to pass wealth to. You, the people, are my family and your happiness is the reason that I stay in politics," Park said.

"Like a mother who dedicates her life to her family, I will become the president who takes care of the lives of each one of you.

"Please open a new era under the country's first female president with hope for change and reform," she said.

Moon was viewed as more combative at a similar event, slamming Park's ruling New Frontier Party as corrupt and incompetent.

"If you spare them punishment, past wrongs will be extended. We have to take up the cudgel and tomorrow is the very day to do so," Moon said, making a special appeal for a strong turnout.

Moon is popular with younger voters while Park's natural constituency is among older, more conservative citizens, especially those who admired her father.

As older voters traditionally turn out in force, Moon's campaign has pushed hard to ensure his supporters do likewise.

Polling booths open at 6 am on Wednesday and close at 6 pm.