By-elections for the Seoul and Busan mayors will be held in April next year after the posts were left vacant by two ruling party members who were accused of sexual misconduct.

Under the constitution of the Democratic Party of Korea, the party cannot field candidates in the by-elections. The internal rule prohibits the party from fielding a candidate in a by-election called after a Democratic Party member loses the elected seat over “serious wrongdoing.”

But the party was set to revise its constitution Tuesday afternoon to make it possible to nominate candidates in the by-elections.

As a pretext to do that, it conducted a poll of all of its members Saturday and Sunday, and said Monday that 86.64 percent of them supported the revision.

In effect, their answer was predetermined early on. Prior to the poll, the party’s Chairman Lee Nak-yon had given them a sort of guideline, saying it is a duty of a responsible political party to field its candidates in elections. Most of the party members who cast ballots are loyal to President Moon Jae-in, and they were already demanding the party nominate its candidates in the by-elections.

The party said it would decide on whether to nominate candidates based on the poll results. Voter turnout was 26.35 percent, short of the quorum (one-third of eligible voters) specified in the party’s constitution. Then the party said the poll was merely a way to sound out its members on the revision. The poll was nothing more than a formality to field candidates in the Seoul and Busan mayoral by-elections.

The clause was written into the party constitution in September 2015 when President Moon Jae-in led the party.

On the campaign trail in an October 2015 by-election for a county mayoral position, Moon said: “This by-election is held because the election of the candidate of the Saenuri Party (one of the parties preceding the main opposition People Power Party) was invalidated for violating the election law. The party should take responsibility, shouldn’t it? It should not field its candidate in the by-election.”

As Moon asserted, the New Politics Alliance for Democracy (one of the ruling party’s precedents) adopted the clause in question. And the party boasted the rule to emphasize its moral superiority to the Saenuri Party. But the party has come to eat its words as it faces a situation in which it would have to follow the clause.

Moon keeps silent as he watches his party overturn the clause made at his request. He clamors for reform, justice and fairness only when the situation is favorable, but hides behind the party or his loyalists when it becomes unfavorable.

Lee emphasized that it is a duty for a political party to be judged by citizens through the nomination of its candidate, and apologized to the people of Seoul and Busan for the by-elections to be held due to wrongdoings by members of his party.

While apologizing on one hand, he argues on the other that the party must field its candidates in the by-elections without failure. It is questionable if the apology is sincere.

A more important duty than its candidates being judged by voters is to keep its promises to them. It must not flip on its guarantee for the party’s own interests.

It is not the first time the party has gone back on its word.

When the Democratic Party pushed through a bill to revise the election law, it vowed not to create a satellite party that would field candidates only for proportional representation seats in the April 15 general elections. But later it broke the promise when opposition parties were expected to take proportional representation seats through their own satellite parties.

When it legislated a bill to create the Corruption Investigation Office for High-ranking Officials, it conceded a veto of candidates for the office head to opposition parties. Now it is moving to eliminate the veto.

On the back of its overwhelming majority in the parliament, the ruling party flips its positions for its own convenience. It is at once unprincipled and shameless.