It cannot be a mere coincidence that President Lee Myung-bak joined his predecessors when he offered a public apology on the corruption of some of his kin and his closest political allies on Tuesday.

Quite a few claim that it is not just personal weaknesses but built-in flaws in the nation’s presidential system of governance that are responsible for corruption among those close to the president. Most notable among them is the concentration of power in what is dubbed the imperial presidency.

That said, corruption cases involving Lee’s kin and close supporters have truly been disappointing to those who believed him when he promised to make his administration cleaner that its predecessors. But the seeds of corruption had already been planted ― even before he launched his administration.

His older brother, Lee Sang-deuk, and Choi See-joong, who was considered his political mentor, allegedly took huge sums of money from businesses during the run-up to the 2007 presidential election. Part of the money, if not all, was suspected of finding its way into Lee’s campaign coffers. Choi’s defense counsel recently told the court that he took the money to support Lee’s nomination.

Lee should have learned a lesson from his predecessors, Kim Young-sam and Kim Dae-jung in particular, each of whom saw his son sent to prison for bribery. But he didn’t. The consequence was that he had to apologize twice on corruption cases involving his relatives and supporters ― this time and in February. It is anyone’s guess how many more will face bribery charges.

Commenting on Lee’s latest apology, the ruling Saenuri Party said a system should be established to shield those close to the president from the temptation to take money from business concerns. Few would dispute that the nation needs new preventive mechanisms, both legal and institutional. But this is easier said than done, given that it would require new legislation and even a constitutional revision.

This is not to say that the political community should sit idly by. Instead, the ruling and opposition parties may well take up such a proposal to establish a new law-enforcement agency empowered to investigate cases involving the presidential kin, aides and other powerful figures and prosecute errant ones.

Aside from proposed institutional improvements, each presidential hopeful will have to take extra caution against receiving illegal contributions from businesses if he or she wishes to avoid following Lee’s footsteps.