Dissidents in Malaysia's ruling party demanded the prime minister's resignation Wednesday after opposition leader Anwar Ibrahim returned to Parliament with a sweeping election victory. Anwar regained his Parliament seat in the north by a landslide in Tuesday's by-election, delivering a demoralizing defeat for the government. Anwar's feat came on the heels of massive gains the opposition made in the March general elections. Prime Minister Abdullah Ahmad Badawi had hoped to make amends in Tuesday's poll. Veteran government lawmaker Razaleigh Hamzah, who wants to challenge Abdullah for the leadership of the United Malays National Organization ruling party, said the results meant that “what scraps of credibility (Abdullah) had left after March 8 are gone.” “It is time to face the music: it is we who have been buried,” Razaleigh said. Former Prime Minister Mahathir Mohamad, who has slammed his successor's policies after handing power in 2003, said he believed many government supporters voted for Anwar “so that Abdullah will realize that his leadership is no longer wanted.” A spokesperson for Abdullah's office could not immediately be reached Wednesday. Government leaders had mounted a fierce campaign to deny Anwar victory, hoping voters in Anwar's longtime bedrock of support would desert the charismatic politician after he was charged with sodomizing his 23-year-old former male aide. No date has been set for a trial. Anwar says the “most sickening” allegation is politically motivated. His election victory has boosted his chances of toppling Abdullah's government through parliamentary defections, which he has vowed to do by Sept. 16. In the March elections, Anwar's three-party alliance won an unprecedented 82 of parliament's 222 seats – 30 short of a majority – and wrested control of five states. Parliament Speaker Pandikar Amin Mulia said Anwar would be formally sworn in as a lawmaker Thursday. Opposition parties also planned to endorse him formally as their leader ahead of a key parliamentary session Friday, when Abdullah announces the annual budget. Mukhriz Mahathir, Mahathir's lawmaker son, said that “with Anwar Ibrahim in Parliament, we cannot afford to have a weak leadership because it could lead to our downfall.” “The walls are crumbling but the top guy seems oblivious to his surroundings,” he said. Government supporters also vented their fury on Internet forums. Mykmu Net, a popular Web site for ruling party members, published comments by readers who said they “hope (Abdullah) will be quickly ousted” and that Abdullah's “resignation will be the only way out.” Abdullah has repeatedly resisted calls to resign immediately after the March elections, though he has pledged to hand power to his deputy, Najib Razak, by mid-2010 in a protracted transition plan publicly endorsed by most top government officials.