Seoul Mayor Oh Se-hoon resigned Friday, taking responsibility for Wednesday’s invalidated free lunch referendum. With his prompt resignation, a by-election will be held on Oct. 26, setting the stage for another battle on welfare between the ruling Grand National Party and the main opposition Democratic Party.

While the two parties fought over one single welfare issue ― free meals for elementary and junior high students ― in the referendum, they are likely to fight this time over more important issues, such as health care, child care and support for elderly people. In this regard, they need to present a comprehensive, coherent and sustainable welfare program to the citizens.

When it comes to specific welfare proposals, the DP is one step ahead of the ruling GNP. The opposition party has the so-called “3+1” package ― free lunches, free health care, free child care plus half-price tuition. Yet the party’s welfare platform is still a work in progress.

As a step toward finalizing its policy, the party will today announce a final version of the “3+1” package complete with a funding plan. Earlier this year, the party drew fire by unveiling a half-baked plan without a detailed financing scheme. It plans to upgrade the package to a “3+3” plan by adding proposals for non-regular workers and housing welfare.

But the DP’s proposals will have to be carefully scrutinized to determine whether they are sustainable. In January, the party suggested that its “3+1” package would require 16.4 trillion won for five years from 2013. Welfare experts, however, said the party grossly underestimated the costs involved.

The opposition party enters this crucial fight over the Seoul mayorship with an important advantage. The referendum victory has enabled it to claim that the public has endorsed its “universalist” welfare policy against the GNP’s “selective” approach. The party will maintain this frame for the by-election, defining the GNP as an “anti-welfare” political group.

While the DP has already started its offensive, the ruling party has yet to get its act together. It has no specific welfare proposals to speak of. Split into two opposing groups, the party is unable to agree on anything. While one group insists that the GNP maintain the present policy of limiting welfare benefits to the needy, the other holds that such a rigid stance is a recipe for defeat.

With the by-election just two months away, it is questionable that the ruling party can overcome its internal division and come up with a coherent blueprint. The party needs to start a debate immediately to thrash out differences. In seeking to forge a consensus, the party needs to heed the outcome of a survey conducted after the lunch referendum.

The survey found that 55.6 percent of the Seoul citizens still supported the selective proposal put forward by Mayor Oh, while those endorsing the DP’s scheme accounted for 38.1 percent. This clearly shows which way the ruling party should go. It should draft a sustainable platform that appeals to a broader swathe of the electorate.