Today, Mr. Mahathir bin Mohamad steps down as prime minister of Malaysia. It has been a remarkable 22 years in office, and his departure marks the end of an era for Malaysia and for Southeast Asia. Mr. Mahathir has been the rarest of species: a visionary and a savvy political realist. He frog-marched his country into the 21st century, looking neither behind him nor to either side. And yet, his legacy will be mixed. Mr Mahathir modernized Malaysia, but development was uneven. His political achievements outstrip those of his country. His successor, Deputy Prime Minister Abdullah bin Ahmad Badawi, will be hard-pressed to overcome the divisions Mr. Mahathir has left. The prime minister's shoes may prove to be too big to fill.

Mr. Mahathir was a physician in the state of Kedah when he first won election to Parliament in 1964. He toiled for a decade before winning a senior post in the ruling United Malay National Organization, which has been in power since Malaysia won independence in 1957. He became prime minister in 1981 and has ruled continuously ever since. Unlike many other Southeast Asian strongmen, Mr. Mahathir left office voluntarily. He announced his resignation in a tearful speech at the UMNO congress in June 2002, and has been working on the transition.

Mr. Mahathir's accomplishments are twofold. Domestically, he has overseen the development of his country from an imperial backwater to a cutting-edge competitor. Malaysia is a successful multicultural democracy -- and an Islamic one at that. It is often held out as the model of a modern Islamic state. He has maintained the peace in an ethnically divided country. That alone is a tremendous achievement -- many say his most important one -- given the poisonous racial legacy left by the British.