By the mid-1990s, it became clear that the most serious threat to Mahathir's power was Anwar's leadership ambition. Anwar began to distance himself from Mahathir, overtly promoting his superior religious credentials and appearing to suggest he favoured loosening the restrictions on civil liberties that had become a hallmark of Mahathir's premiership. However, Mahathir continued to back Anwar as his successor until their relationship collapsed dramatically during the Asian financial crisis. Their positions gradually diverged, with Mahathir abandoning the tight monetary and fiscal policies urged by the IMF. At the UMNO General Assembly in 1998, a leading Anwar supporter, Ahmad Zahid Hamidi, criticised the government for not doing enough to combat corruption and cronyism. As Mahathir took the reins of Malaysia's economic policy over the coming months, Anwar was increasingly sidelined. On 2 September, he was dismissed as deputy prime minister and finance minister and promptly expelled from UMNO. No immediate reasons were given for the dismissal. However, the media speculated that it related to lurid allegations of sexual misconduct circulated in a "poison pen letter" at the general assembly. As more allegations surfaced, large public rallies were held in support of Anwar. On 20 September, he was arrested and placed in detention under the Internal Security Act.