Politicians tend to ignore common sense when they pursue their own partisan interests. This attitude gets more serious when they quarrel over highly sensitive political issues.

One good example is the ongoing dispute over the possible appointment of an independent counsel for the Sung Woan-jong scandal.

There is no reason to oppose the idea if it is purely intended to ensure an independent, fair and thorough investigation into the case, which involves ― among other things ― the former prime minister, close aides to President Park Geun-hye and her past election funds.

To be fair, the prosecution’s investigation ― due to or despite its magnitude ― has made little progress since Sung died 20 days ago after leaving a memo containing the names of eight politicians, some of whom he also mentioned in a recorded telephone talk with a journalist.

Prosecutors have yet to summon any of the eight politicians, even though they arrested two aides to the late Sung, who claimed in the memo and phone talk that he gave money to politicians, including Lee Wan-koo who officially resigned as prime minister Monday, Park’s former chief of staff and key election managers.

But the slow progress of the probe and the involvement of Park’s former and current key aides are not the only reasons why the rival parties are escalating the war of words on the proposal to name an independent counsel.

There are deeper political motives. The New Politics Alliance for Democracy, bent on taking full advantage of the scandal in attacking the Park government and the ruling party, insists that the case should be handled by a special prosecutor, not by state prosecutors.

The problem is, however, the main opposition party is demanding that the independent counsel be named under a new special legislation, not the current special prosecutor law.

NPAD leader Moon Jae-in said he is insisting on a new legislation because under the current law, the special prosecutor should be appointed by the president. He said that this is absurd because the special prosecutor is supposed to investigate people close to the president and possibly even the president.

But what Moon did not say is that the independent counsel named under the current law has only up to 90 days to complete the probe. This means his party will lose a chance to keep the scandal alive for a long time.

There is no denying that the state prosecution has often faced questions about its political independence and neutrality. The opposition’s demand that the current Blue House chief of staff Lee Byung-kee, one of the eight mentioned in Sung’s memo, should resign so that he cannot influence prosecutors has some grounds.

But if we have to appoint an independent counsel whenever there is a politically and socially sensitive issue, why do we need state prosecutors? Moreover, remember that of the 11 special prosecutors who have been appointed since 1999, few could uncover anything other than that disclosed by authorities like the prosecution.

The prime minister’s official resignation should pave the way wider for prosecutors whose mission is to conduct a fair and thorough probe, and complete it as soon as possible. If the public sees the probe was not fair and thorough, then we could discuss the next steps like a special parliamentary investigation or the appointment of a special prosecutor.