The allegation that UN Secretary-General Ban Ki-moon received money from a businessman should be seen as the start of a vetting war among candidates for the next presidential election.

It also reminds us that Ban, a frontrunner for president who lacks experience in domestic politics, will be subject to harsh scrutiny and rigorous political attacks when he returns home around the middle of next month.

The allegation, reported by the Sisa Journal weekly magazine, said that Ban received $230,000 from Park Yeon-cha, former CEO of Taekwang Industries who once was at the center of a corruption scandal involving the late President Roh Moo-hyun.

The report, quoting anonymous sources, alleged that Ban -- then foreign minister under Roh -- received $200,000 from Park, then honorary consul general of Vietnam, in May of 2005 when he hosted dinner for the visiting Vietnamese foreign minister in his official residence in Seoul.

The report also said Park gave Ban -- the then-UN secretary-general -- $30,000 through a proprietor of a Korean restaurant in New York in January of 2007.

Ban, speaking through a UN spokesperson in New York and an associate in Seoul, flatly denied the allegation as “completely false and groundless.” Park also said he did not give money to Ban.

Ban needs to personally clarify his position upon his return home, and he must take legal action against the magazine, because the allegation would be unable to be verified without an investigation by a legitimate law-enforcement authority.

We advise this because as one of the frontrunners, running neck and neck with Moon Jae-in of the Democratic Party, Ban should be ready to brace for more allegations.

Ban does not have experience in domestic politics and has never gone through meticulous public scrutiny. For instance, when he was appointed foreign minister by Roh in 2004, there was no parliamentary confirmation hearing for the post.

Ban and other potential candidates, including Moon, should be reminded that the currently unfolding Choi Soon-sil scandal will call for a more thorough qualification check on candidates than ever before.

The Choi scandal vividly shows that we failed to uncover President Park’s suspicious ties with the Choi family, even though they started in the 1970s. This resulted in the national fiasco we have been going through for months.

It had been well known to the public that President Park, after her mother was assassinated by a Korean-Japanese sent by North Korea in 1974, began developing a relationship with Choi Tae-min, the late father of the central figure in the current scandal.

As it turned out, her ties to the family continued through the daughter. This calls on us to search our soul because Park went through numerous elections since 1998 when she was first elected to the National Assembly.

She was elected to the parliament four more times, and most recently ran in two presidential elections -- first in 2007 when she lost party nomination to Lee Myung-bak and second in the 2012 successful bid to take presidency.

If there had been anyone who could shed light on the close personal relationship with President Park and the Choi family through any of the elections, she would never have won the 2012 election, and at the least, would have never allowed the woman who does not have any official credentials to peddle influence and interfere in state and presidential affairs.

The likelihood that the next presidential election could be held much earlier than December next year raises concerns about the usually poor checks on the candidates’ qualifications.

The Constitutional Court’s upholding of the parliamentary impeachment of Park would give the nation only two months for the election, which would certainly put candidates, parties and voters in a rush.

That may also mean that the upcoming vetting war would be fiercer, with candidates who want to see the popularity of their rivals diminish resorting to indiscriminate mudslinging and smear campaigns.

This offers a bigger cause for concern, given the fact that there were even cases cooked up or fabricated to damage opponents. The prime example is the case of Lee Hoi-chang, who lost his presidential bid in 1997 and 2002, partly due to the opposition’s attacks over the exemption of military service of his sons.

Of course, it is tricky to strike a balance between thorough vetting and ensuring fairness and reasonableness. Most of all, the election watchdog and law-enforcement authorities should get tough and respond quickly to any acts of a smear campaign and accusations that lack evidence.

Media and voters should also be sensible enough to tell reasonable questions about candidate qualifications from malicious accusations. One thing that is certain is that the candidate vetting process should never repeat the failure of four years ago.