"I think it is an important objective, and I think we can reach it," said Judiciary Committee Chairman Arlen Specter, R-Pa., who said he doesn't expect Democrats to filibuster a Supreme Court nominee.
Democrats, however, said they wouldn't be rushed, considering that O'Connor said in her resignation statement that she would serve until her replacement was confirmed.
"We have plenty of time," said Sen. Charles Schumer, D-N.Y.
Specter will control the confirmation hearings, a task his staffers have been working on for months. Republican staffers speculate that initial hearings won't begin until a month to six weeks after President Bush nominates a successor to give senators time to do their own investigations of the nominee.
Mr. Bush will not make a nomination before July 8, the White House said, pushing any possible hearings back until August at the earliest if Specter follows that timetable.
Senators have not decided how to limit the number of witnesses, and GOP staffers have said hearings could go on for at least a week or more to accommodate senators, the nominee and the witnesses.
At the conclusion of the hearings, Specter will call a committee vote at the next available committee meeting. While Democrats have said they expect to question the nominee thoroughly, Supreme Court nominations traditionally advance to the full Senate for a vote even if they get negative recommendations from the Judiciary Committee.
If the nomination is controversial, Senate Majority Leader Bill Frist, R-Tenn., will likely have to decide whether to try to prevent Democrats from using a filibuster to block confirmation.
"If a few senators refuse to grant the president and his nominee that courtesy, I would encourage Majority Leader Frist to restore the Senate's 214-year-old precedent that gave judges the basic right of vote," said Sen. Tom Coburn, R-Okla.
Seven Democrats and seven Republicans have signed a pact not to filibuster judicial nominees except in extraordinary circumstances. At the same time, they agreed to oppose attempts by GOP leaders to change filibuster procedures.
Frist was giving a speech on prescription drugs on the Senate floor when the announcement was made. He quickly shifted gears and began praising O'Connor's career.
Meanwhile, conservative and liberal groups sprang into action with the word of O'Connor's retirement, telephoning supporters and firing off e-mails to mobilize help for a high-stakes Senate confirmation battle.
People for the American Way, which set up a war room for the Supreme Court battle in downtown Washington, sent out thousands of e-mails to its supporters and was setting up phone banks to make calls around the nation to build up support for Senate Democrats.
"The American people must be part of this great debate over our future," president Ralph Neas said.
Other groups were planning to work the old-fashioned way with protests, rallies and marches on the Supreme Court and the Capitol. "We will not go silently into the night concerning the appointment of Supreme Court justices and plan a major presence outside the court and halls of Congress," said Rev. Patrick J. Mahoney, director of the Christian Defense Coalition.
MoveOn PAC announced a cable television ad campaign $280,000, a relatively small amount in Maine, Nebraska, South Carolina, Virginia, New York City and Washington, D.C., trying to discourage Bush from picking a strict conservative.
"Will George Bush pick an extremist who will threaten our rights?" the commercial asks.
Abortion-rights groups like Planned Parenthood already are scheduling rallies in an effort to influence Mr. Bush's choice. "With so much at stake, Planned Parenthood will be on the front lines of the Supreme Court battles to ensure women's health is protected," said interim president Karen Pearl.
Progress for America has said it expects to spend $18 million to get Mr. Bush's nominee confirmed to the Supreme Court, and has already started running television and radio ads around the nation.