With John Roberts' confirmation as chief justice now assured, Republicans on Tuesday began pressuring the Senate's minority Democrats to promise what they called a fair confirmation hearing and vote for President Bush's next Supreme Court (search) nominee.

Bush could announce his choice to replace retiring Justice Sandra Day O'Connor (search) as early as Thursday, the same day the senators plan to overwhelmingly confirm Roberts as the Supreme Court's 17th chief justice.

Almost three-fourths of the 100-member Senate will vote for Roberts, a 50-year-old conservative U.S. Appeals judge and former appellate lawyer, as the replacement for William H. Rehnquist (search), who died earlier this month.

"If being intelligent, brilliant, a superb lawyer, the greatest legal mind of your generation and well qualified is not enough, what is?" said Sen. Lindsey Graham (search), R-S.C., a member of the Senate Judiciary Committee.

While Roberts is assured his seat, confirmation could be tougher for O'Connor's replacement. She often has been a swing vote, a majority maker whose replacement could signal a shift on the court on many contentious issues including abortion and affirmative action.

Democrats have successfully filibustered several of Bush's conservative choices for lower courts, and Republicans are jumping out front to try and dissuade them from attempting to do the same to Bush's next pick, who probably will be someone more conservative than O'Connor.

"Because the nominee might be perceived by some to be more conservative in their view than Justice O'Connor, somebody is going to make the argument that this then makes this more extraordinary, and therefore try to put pressure on Democrats who have not seen fit to filibuster judicial nominees to say, 'Well, this is different,'" said Sen. Jon Kyl (search), R-Ariz., chairman of the Senate Republican Policy Committee.

Added Sen. Mitch McConnell (search) of Kentucky, the Senate's No. 2 Republican: "On this particular nomination we conducted ourselves well, and hopefully we can do that again since we'll have another nominee."

The White House is on the verge of completing its consultation with the Senate on the second seat, spokesman Scott McClellan (search) said Tuesday. As many as 70 senators have been contacted, as have most of the 18 Judiciary Committee members, he said.

Democrats contended on the Roberts nomination that the White House did not do enough consultation. Senate Democratic leader Harry Reid (search) of Nevada said he would reserve judgment on how the consultation has gone for the second seat.

"We'll see who they give us, and that'll answer that question," Reid said. "You don't need a lot of consultation if the person you're consulting with listens to you, so we'll see."

Democrats are pushing for the White House to name a "mainstream" conservative to O'Connor's seat. The president is also under pressure from many quarters — including his wife — to pick a woman or a minority candidate.

Sen. Ken Salazar (search), D-Colo., one of Roberts' supporters, urged the president not to "allow the clock of progress for our country, and in particular for women, to be turned back by diminishing the number of women on the court."

Salazar, one of two Hispanic senators, also called for Bush to consider nominating the Supreme Court's first Hispanic justice. It would be "a historical appointment," he said in a letter to the White House.

Widely mentioned candidates for O'Connor's seat include federal appellate judges Janice Rogers Brown, Edith Brown Clement, Edith Hollan Jones, Emilio Garza, Alice Batchelder, Karen Williams, J. Michael Luttig, J. Harvie Wilkinson, Michael McConnell and Samuel Alito. Attorney General Alberto Gonzales, former deputy attorney general Larry Thompson, lawyer Miguel Estrada and Maura Corrigan, a member of the Michigan Supreme Court, are also considered possibilities.

Democrats opposing Roberts say they're concerned the former lawyer in the Reagan and George H.W. Bush administrations will be staunchly conservative like Justices Clarence Thomas and Antonin Scalia.

"He has not convinced me that he will not uphold just the letter of the Constitution, but the spirit of the Constitution as well," said Sen. Jack Reed (search), D-R.I.

Roberts' supporters say they're not worried about whether he is conservative.

"To vote against Judge Roberts, I would need to believe either that he were an ideologue whose ideology distorts his judgment and brings into question his fairness and open-mindedness or that his policy values were inconsistent with fundamental principles of American law," said Sen. Carl Levin (search), D-Mich. "I do not believe either to be the case."