When the obituaries come to be written for Dr Mahathir Mohamad, Malaysia's prime minister from 1981 to 2003, they were always going to be mixed. The man who put his country "on the map", according to a former Asian Wall Street Journal editor, Barry Wain, and whom the Far Eastern Economic Review hailed as "a new voice for the Third World", was also too blunt and outspoken for his critics in the West. He oversaw a period of stunning growth, but corruption grew on his watch while the judiciary became so tarnished that one senior jurist observed in 2001: "It used to be that the tinting of judges' cars was for security, but now I say it is to hide my embarrassment." The courts may have since recovered their independence, but today Mahathir's continued involvement in politics, well into his retirement, has reached the stage that he is in severe danger of undermining his own legacy completely. He has already helped unseat one prime minister, his handpicked successor, Abdullah Badawi. Few shed many tears over that; kind and pious he may have been, but Badawi was widely regarded as ineffective. Currently, though, Mahathir appears to be doing everything he can to sabotage the position of Badawi's successor, Najib Razak. This is another matter completely, as Najib is a pragmatic moderate who has won plaudits both for his steering of the economy - last year foreign direct investment in Malaysia was the highest ever, and the country is on course to reach developed nation status by 2020 - and for his diplomatic initiatives, such as helping negotiate the historic Bangsamoro peace deal in the Philippines and brokering the political solution to the Malaysia Airlines Flight 17 tragedy. For Mahathir, however, this is not enough. Having publicly withdrawn his support from Najib in August, he - or his proxies - tried and failed to foment a rebellion against the premier last month at the general assembly of Umno, the lead party in the ruling National Front coalition. His hand is believed to have been behind a police report filed this month in connection to a state investment fund closely associated with the prime minister; and also a brazen attack at a conference of the hardline Malay rights group Perkasa, to which Mahathir is adviser, during which its leader warned Najib that he risked losing "your post and the government" if he didn't cut down on his overseas trips. This is hugely damaging to Umno, the party to which Mahathir has belonged, apart from two short periods, for more than 50 years. Mischief-making and attempts to divide also have the potential to cause great harm to the National Front, which has been struggling to maintain levels of support in a country whose ethnic and religious diversity can also be exploited by chauvinist actors - such as Perkasa, a group so extreme that even Mahathir's activist daughter Marina says "they talk such rubbish". The National Front has, in one form or another, won every election since independence in 1957. If it were to lose power because of his machinations, Mahathir would have helped bring down the coalition he himself had led for so long. That would be a disastrous coda to his political life. I write as an admirer of Mahathir, one of very few Western journalists, I imagine, to have concluded an interview with him by asking him to sign a copy of his inflammatory 1970 tract, The Malay Dilemma . But for the good of his party, the National Front, and for himself too - he is 89 - it is surely time for Mahathir to take a back seat. Let his legacy be his successes in office and on the international stage. It would be a shame if he were to be remembered more for stirring dissent behind the scenes when his successors failed to pay sufficient attention to his advice. Sholto Byrnes is a Kuala Lumpur-based commentator