Now Mr. Uribe's very success threatens to become his undoing. Four years ago his political supporters led a movement to amend the constitution so that he could serve another term; the president won reelection in a landslide. Now, with his second term due to expire in 2010, another such movement has appeared. Last week, the Colombian Senate approved a constitutional amendment that, if reconciled with a version in the lower house and approved by the country's supreme court, could be put to a public referendum this year. Polls show that Mr. Uribe remains extremely popular and would be likely to win a third term.
That means that Mr. Uribe -- who has not yet said whether he will seek to remain in office -- must be challenged to undertake what might be his most impressive feat yet. He should exercise the check on himself that Colombia voters would forgo and step down after his current term ends. Despite his landmark achievements, his government has been weakened by scandals in the past several years, some of them serious. More than two dozen army soldiers have been arrested for the practice of murdering innocent civilians and depicting them as guerrillas; the intelligence service is under investigation for spying on opposition politicians and journalists. Though Mr. Uribe has not been personally implicated in the scandals, two of his sons have recently been the target of corruption charges.
The most compelling reason for his retirement, however, is to strengthen Colombia's democratic institutions. With its vibrant press, independent courts and active civil society, the country stands out as an alternative to the populist autocracy established in neighboring Venezuela. After two tries, Hugo Chávez recently eliminated the limit on his own tenure and now is seeking to destroy what remains of his opposition. In a region plagued by misrule, Mr. Uribe has demonstrated how much a capable elected president can accomplish; now he has the chance to show the importance of placing institutions and the rule of law above any one leader.
Mr. Uribe said recently that he is conflicted about a reelection bid; while acknowledging that it might weaken democracy, he said he is worried about preserving his "democratic security" policy. But at least one worthy successor is available: Defense Minister Juan Manuel Santos recently resigned and said he would run for president if Mr. Uribe did not. If he remains in office, Mr. Uribe would run the risk of undermining his own successes; some of his strongest supporters could turn against him, and the good relations he has enjoyed with the United States could come under strain. Better that the president choose to step down and give his country a last great gift, by strengthening the political system he has fought so hard to save.