US: Senator Hillary Rodham Clinton and three other Democrats believed to have presidential ambitions in 2008 will vote against John Roberts's nomination as US chief justice this week.
Mr Roberts is almost certain to be confirmed, however, with the support of many Democrats along with the Senate's Republican majority.
As senators debated his nomination, many looked ahead to President Bush's nomination, expected by Friday, of another supreme court judge to succeed Sandra Day O'Connor. A number of senators urged Mr Bush to replace Ms O'Connor with another woman or a member of an ethnic minority.
Senators John Kerry, Joseph Biden and Evan Bayh joined Ms Clinton in signalling that they would vote against Mr Roberts, citing the nominee's refusal to answer some questions during Senate hearings earlier this month.
Ms Clinton said it remained unclear if Mr Roberts still supported conservative positions expressed in memos he wrote during the administrations of Ronald Reagan and George H W Bush. Mr Bayh said the hearings served to deepen ambiguity surrounding Mr Roberts's attitude to issues such as civil rights, rather than resolving it.
"Voting to confirm a nominee to the Supreme Court must be more than an act of faith. We simply do not know enough about his views on critical issues to make a considered judgment."
Mr Biden, who questioned Mr Roberts during the judge's appearance before the Senate judiciary committee, described as "a close call" his decision to oppose the nomination.
"In my view, he did not provide to the American people any assurances that he embraced fully the constitution's enduring values when it comes to fundamental constitutional rights," he said.
Republicans accused the Democratic presidential hopefuls of pandering to liberal interest groups which could be an important source of funding during a future campaign. Civil rights and women's rights groups fear that Mr Roberts could encourage the supreme court to roll back legislation that guarantees affirmative action in favour of underprivileged minorities and abortion rights for women.
Republican senator Orrin Hatch accused Democrats of opposing Mr Roberts "in large part to somehow send a message to President Bush as he deliberates on how to fill the remaining vacancy on the supreme court".
South Dakota's Tim Johnson was among a number of Democratic senators to urge Mr Bush to choose a moderate judge rather than a hardline conservative to fill the remaining seat on the supreme court.
Republican women senators joined their Democratic counterparts in calling for Ms O'Connor's seat to be filled by a woman, who would be one of only two on the supreme court bench.
Mr Bush hinted this week that he will nominate a woman or a member of an ethnic minority.
