From the first day in office, the next president, who will begin a five-year term in February, will have to grapple with a complicated mixture of security and diplomatic tasks. Successfully handling them would be crucial to ensuring peace and prosperity for the country.

The successor to President Lee Myung-bak will face tougher external conditions. Navigating them will need long-term strategies, sophisticated tactics, diplomatic discretion and, in some situations, firm determination.

North Korea, under its young hereditary ruler Kim Jong-un, remains as unpredictable as ever, preparing to launch what it claims to be a satellite rocket between Dec. 10 and 22. The 13-day window set by Pyongyang is overlapped both with the first anniversary of the death of Kim Jong-un’s father, Kim Jong-il, on Dec. 17 and the Dec. 19 presidential election in South Korea.

Over the coming years or decades, Seoul will have to walk a fine line between the U.S. and China, which are in an escalating rivalry over hegemony in the Asia-Pacific, to be best positioned to secure its interests. It will be another diplomatic challenge to handle a Japanese government with an ultra right-wing agenda, which is expected to emerge as a result of the parliamentary election on Dec. 16.

Park Geun-hye, the presidential candidate of the ruling Saenuri Party, was right to say that the next five years would be a crucial period in diplomatic and security terms during her TV debate on Tuesday with her two opposition contenders ― Rep. Moon Jae-in of the Democratic United Party and Lee Jung-hee of the Unified Progressive Party.

The debate, the first of three sessions set among the three candidates, was held on the topics of political reform, foreign affairs, security and inter-Korean relations. It would have been more appropriate for the debate to be arranged in a way to ensure intense discussion between the two major candidates ― Park and Moon ― on the critical security and diplomatic challenges facing the nation. Election officials may need to consider changing the current rules to bar a distant third runner from joining what should be a serious debate between the main contenders, only to blur its focus, as shown in Tuesday’s session.

Even though they did not manage to fully assure voters of their ability to handle critical security and diplomatic matters, Park and Moon expressed views that departed from the dichotomous and rigid approaches taken by the previous administrations.

They struck somewhat different tones on dealing with threats from North Korea and looking for a proper route through the mounting confrontation between the U.S. and China, but they still showed possibilities for bridging the gap between their stances.

It was noteworthy that Park, backed by conservatives, made it clear she would attach no strings to resuming talks with North Korea, while Moon, representing the liberal bloc, urged Pyongyang to scrap its rocket launch plan. They also shared the perception that Seoul should be more balanced in its ties with Washington and Beijing by maintaining a close alliance with the U.S. and expanding a friendly partnership with China.

The two main presidential contenders should try to secure as much common ground as possible for dealing with inter-Korean relations and other security and diplomatic tasks. Though with limited scope, a suprapartisan approach will be needed to keep Pyongyang in check and increase Seoul’s leeway between the U.S. and China. It should be reminded that both the unconditional engagement and the rigid adherence to the principle of reciprocity ― pursued by the liberal and conservative administrations in Seoul over the past decade ― went nowhere in changing North Korea toward reform and openness.

During Tuesday’s debate, Park and Moon expressed their willingness to pass political reform bills through parliament before the presidential election. They should recognize that such bipartisan cooperation is most needed in the security and diplomatic fields to consolidate the foundation for the stability and prosperity of the nation.