Long bitter enemies, Malaysia's Anwar and Mahathir join forces against premier Najib

By Joseph Sipalan and Praveen Menon KUALA LUMPUR (Reuters) - Anwar Ibrahim, the imprisoned de-facto leader of Malaysia's opposition alliance, has endorsed a political compact spearheaded by his arch-nemesis Mahathir Mohamad, as ruling party rebels and the opposition join hands to fight against scandal-tainted Prime Minister Najib Razak. This new coalition could potentially pose the biggest political threat to Najib, who has been facing persistent calls to step down over multi-billion dollar graft allegations tied to the state-owned investment fund 1Malaysia Development Berhad (1MDB) that he oversaw. Both Anwar and former premier Mahathir have long been central figures in Malaysian politics.