In Congress, on courthouse steps and in newsrooms across America, the buzz was that one of the nine Supreme Court judges was about to resign. It seemed to make sense that it would be Chief Justice William Rehnquist, a staunchly conservative octogenarian whose struggle with throat cancer has left him frail and barely able to speak. But the announcement two weeks ago that it was swing-voter Sandra Day O'Connor, a moderate who has rejected political and religious ideologies and kept the bench centred, has sparked what is likely to be a bruising succession contest. Her departure creates the first Supreme Court vacancy in 11 years. The task of nominating her replacement rests with President George W. Bush. But the task of confirming that choice rests with the Senate, where Democrats have the power to block any nomination they consider too conservative. 'We are contemplating how we are going to go to war over this,' third-ranking Democratic Senator Charles Schumer, and also a member of the Senate Judiciary Committee, was overheard telling a colleague last week. The Supreme Court is the United States' most powerful judicial institution, shaping the social landscape with landmark rulings such as Brown vs Board of Education in 1954, which abolished racial segregation in schools, and Roe vs Wade in 1973, which legalised abortion. Underlining its role in settling some of the nation's most religiously charged issues, it has more recently been called on to rule on matters such as whether the Ten Commandments may be displayed at public courthouses and whether gay marriage should be legal. Appointments to the Supreme Court bench are for life, making the selection process all the more critical as groups across the political spectrum lobby for a nominee who will best advance their agendas. Abortion, one of the country's most polarising issues, is among the leading concerns. Also on the list are affirmative action, the separation of church and state and the right to detain terrorist suspects indefinitely - all issues on which Justice O'Connor, who was nominated by the Republican president Ronald Reagan, cast the deciding vote for the liberal position. Mr Bush's Christian conservative voter base is pressing for a more right-wing thinker with a tougher 'pro-family' and 'pro-life' stance. Many favour Judge Michael McConnell, of the 10th US District Court of Appeals in Denver, an anti-abortion father of three. He once sided with the Boy Scouts of America when it appealed for homosexuals to be barred from their organisation, and described Roe vs Wade as 'an embarrassment'. But his condemnation of the Supreme Court's ruling in 2000 that resulted in Mr Bush being declared president over Democratic opponent Al Gore could sit uncomfortably with many conservatives - and the White House. Instead, many Republicans favour hardline appeals judge John Roberts, former legal counsel to President Reagan. As deputy attorney-general under president George Bush Snr, he drafted legislation that cut off federal funding for doctors who referred patients to abortion clinics. Alternatively, there is Judge Michael Luttig, 50, of the 4th US Circuit Court of Appeals in Richmond, Virginia. Doubts remain, however, as to whether he would toe the line closely enough - he once upheld a state ban on the controversial practice of 'partial birth abortion', but later overturned it. Others think that Mr Bush, anxious to avoid a Senate wrangle, could plump for centrists who Democrats would find more palatable. The shortlist includes US Attorney-General Alberto Gonzales, a close friend of Mr Bush. Mr Gonzales would become the first Hispanic Supreme Court judge, appealing to a fast-growing voter bloc but dampening the enthusiasm of conservatives. The president has assured Democrats he will not be applying any political 'litmus test' to find a candidate. 'I'll pick people who, one, can do the job, people who are honest, people who are bright and people who will strictly interpret the constitution,' he said. But many doubt it. The tussle is 'guaranteed to be knock-down, drag-out, wall-to-wall ugly', predicted Brent Bozell, of the Media Research Centre in Washington.