President Lee Myung-bak must have been dejected last week when he saw his older brother, Lee Sang-deuk, being sent to jail on television. He must have wondered what had gone wrong.

The same question must have been asked by so many Koreans, who have in the past witnessed some of those close to presidents or presidential candidates being sent to prison for taking bribes and breaching the election-funding law. Lee’s brother, accused of taking money from businesses, may have followed in their footsteps, instead of learning from their experience.

A more important question, however, is: Will TV show similar scenes anytime during the next five years? Possibly it will, if the past experience is any guide.

Lee Sang-deuk, a former lawmaker affiliated with the ruling Saenuri Party, was charged with taking huge sums of money in bribes from savings banks and other business concerns during the run-up to the presidential election in 2007. Large portions of the money, if not all, were allegedly used to bankroll Lee Myung-bak’s campaign.

It has not been unusual in Korean politics for presidential family members, aides and associates to be sent to prison for taking bribes, funding campaigns by illegal means, or both. Responsible for the criminal offenses are individual foibles and institutional drawbacks.

More important, presidential campaign managers and others close to presidential nominees are easy targets of illegal lobbying from corporations. Quite a few corporations, especially those vulnerable to political coercion in one way or another, attempt to bribe them or offer to make large contributions to their campaigns. They launch such lobbying as soon as the main parties select their standard-bearers.

There are also cases in which campaign managers solicit illegal corporate contributions when their coffers are not filled.

Either way, corporations regard the money used for illegal contributions as an insurance premium for protection from the wrath of future presidents. After all, the Korean president is all powerful.

It would not be easy for those managing presidential campaign funds, if not presidential nominees themselves, to keep themselves from the lure of large corporate contributions. They need huge sums of money to finance a presidential campaign ― a costly enterprise, which many suspect cannot be covered by the officially sanctioned amount alone.

The legal limit to a presidential campaign fund for the Dec. 19 election is set at 56 billion ― a large amount that a nominee will have a hard time collecting through legitimate contributions. Still, it may not be large enough for any serious candidate to finance a winning campaign.

Against this backdrop, Rep. Moon Jae-in of the main opposition Democratic United Party is planning to make public offerings to create an electoral fund, as well as taking legitimate contributions, if he wins the party’s nomination. Subscribers will be paid back the principal and the interest when the campaign expenses are refunded by the state after the election.

Public offerings, a fundraising method that was used by Seoul Mayor Park Won-soon and some lawmakers, merit serious consideration by not only Rep. Moon but other presidential hopefuls, given that they will certainly make the campaign-funding process more transparent.

Still, public offerings will not provide any guarantee against illegal contributions. Candidates will certainly be tempted to take illegal contributions if they believe the legally permissible maximum amount of campaign money, let alone the amount raised through public offerings, is not large enough to mount a successful bid for the presidency.

Indeed, many electoral experts are already saying 56 billion won will not be large enough to cover all campaign expenses. If so, it is necessary to revise the election-funding law so that the National Election Commission can increase the legal limit. But that is not technically possible, with only four months left until the presidential vote.

For now, one of the few antidotes against illegal financing is the reminder of what will lie ahead if campaign managers fail to toe the line. For this reason as well as others, the prosecution will have to dig deeper into an allegation about illegal contributions to Lee’s presidential campaign. If they are to serve as warning against illegal campaign financing, the prosecutorial proceedings should provide no leniency to any offender this time.