The main opposition Democratic United Party’s presidential hopeful Moon Jae-in and independent candidate Ahn Cheol-soo have agreed in principle to merge their candidacies. If they have made up their minds to field a unified candidate, they need to enter into negotiations immediately and reach an agreement as early as possible.

The two agree that the unified candidate should be chosen by Nov. 24 as candidates are required to register with the National Election Commission on Nov. 25-26.

Yet the two are still at odds over when to start talks as the timing of negotiations could determine the method of candidate unification, which in turn could influence the outcome of the unification process.

Moon is keen to launch negotiations without further delay as the selection methods he prefers take time to implement. For instance, he believes he stands a better chance if the candidate is selected through an open primary. But arranging such a vote takes much time.

In contrast, Ahn favors opinion polls as he has maintained a lead over Moon in popularity polls ever since he declared his candidacy. As polls can be conducted with little preparation, there is no need for him to begin negotiations early.

Hence he refuses to engage in talks with Moon before Nov. 10, the day he plans to unveil a much touted election platform. His selection of the date for announcement of the policy package weeks ago suggests he had already decided on how to promote the alliance with the DUP candidate.

Ahn is expected to follow the precedent set 10 years ago by then presidential candidates Roh Moo-hyun and Chung Mong-joon. The two started unification talks on Nov. 9, reached a final agreement on Nov. 22, held a TV debate that night and conducted opinion polls on Nov. 24. The winner was announced hours later.

If Ahn sticks to his own schedule, Moon has no choice but to follow it. This means the DUP candidate will also have to give up the unification methods he prefers because there would not be sufficient time for them.

Yet using opinion polls as the selection method is fraught with problems. When Roh and Chung chose opinion polls to determine the final opposition candidate, major pollsters refused to conduct polls, saying they could not be a substitute for elections.

Picking a candidate only through opinion polls makes the whole election process unnecessary and thus denies the spirit of democracy. The two candidates should bear this point in mind and start talks immediately to find a more suitable way to merge their candidacies.