WASHINGTON – President Bush is widely expected to nominate either Judge Samuel Alito or Judge Michael Luttig to the Supreme Court this morning – two veteran conservatives from the U.S. Circuit Court of Appeals whose emergence as possible replacements for retiring Justice O’Connor would energize the conservatives who helped derail Mr. Bush’s last nominee and almost certainly trigger a vicious Senate fight.

Speculation focused on the two men soon after the White House counsel, Harriet Miers, withdrew from consideration last week. Both are well-known conservatives with stellar academic and professional credentials – qualities that worked well for Mr. Bush’s first nominee, John Roberts, and which appeared all the more important after the doomed nomination of Ms. Miers. Both have also been on Supreme Court short lists for years.

Mr. Bush has repeatedly fooled courts watchers before by floating the names of people he did not ultimately put forward. The nomination of Chief Justice Roberts surprised even some of the president’s closest aides, people familiar with the process said, as did the nomination of Ms. Miers. Judge Alito is widely thought to have been the second choice behind Ms. Miers, one of the reasons many think he will be named to replace her.

Another reason Judge Alito is favored by many is his record of judicial restraint during a 15-year tenure on the Philadelphia-based 3rd Circuit. Judge Luttig, who sits on the Richmond, Va.-based 4th Circuit, also has a record of advocating for judicial restraint. But sources said Judge Luttig’s greater willingness to take controversial stands and his Texas roots could hurt him at a time when the White House is suffering from charges of cronyism and Democrats are poised to pounce on any evidence of immoderacy.

Conservatives could be expected to line up behind the 55-year-old Judge Alito, a graduate of Yale Law School and a former U.S. attorney for the District of New Jersey, or Judge Luttig, a 51-year-old graduate of the University of Virginia Law School who is known as a mentor of young conservative lawyers. Both worked as young lawyers in the Reagan administration and are enthusiastically supported by the conservative activist groups that rebelled against Ms. Miers.

“I’d be satisfied with either Alito or Luttig,” the president of the Free Congress Foundation and a vocal opponent of Ms. Miers, Paul Weyrich, said. “I think the president would do very well if he appointed either one of them. We’ll just have to wait and see.”

Democrats have indicated that they will filibuster any nominee they regard as too conservative. It would require 60 senators to end such a filibuster, though 50 senators could try to break it with a rule change commonly referred to as the “nuclear” or constitutional option.

Conservatives who have been waiting for years for the crucial swing seat occupied by Justice O’Connor to open have said they want a fight. President Bush’s willingness to engage in an open battle with Democrats is not as clear. Also unclear is the willingness of Republican senators to break a filibuster.

“What we really need is a serious fight with people who have absolutely no respect for the Constitution,” a congressman who has been an ally of the Senate Republicans in the judicial confirmation process, Rep. Trent Franks, of Arizona, said in an interview. “What we need is a serious, get-down, clear-the-air, slug-it-out fight so the real issues can be exposed here. If the Democrats want to fight about that, let them fight at their own peril.”

Despite the strong expectation that Judge Alito or Judge Luttig will be picked, a lawyer with close ties to the White House said anticipating a decision ahead of time is unwise. The lawyer, who asked not to be identified because of the sensitivity of the process, said that while Mr. Bush’s penchant for surprises backfired on the last nomination, he is just as likely to make another surprise announcement this time around.

“It’s not a decision until the name passes his lips in public,” he said. “And anyone who has ever worked for a president knows that. I think what people are doing is rewinding the tape – they think Alito was second in line last time, and so they’re saying, ‘If not then, then now.’ But that’s not the way it works.”

One surprise Mr. Bush is not expected to try again is picking a stealth candidate. Other clearly conservative potential nominees include a Federal Court of Appeals judge for the 10th Circuit, Michael McConnell; a federal Court of Appeals judge for the 6th Circuit, Alice Batchelder, and a federal Court of Appeals judge for the 5th Circuit, Edith Jones. A federal Court of Appeals judge for the 4th Circuit whose name has also circulated is Karen Williams, though some social conservatives have expressed concerns about her past recusal from an abortion case.

Several signs pointed to Judge Alito. A White House official who did not want to be identified said that Mr. Bush’s legal team had signed off on a nominee late last week, hours before speculation began to intensify about the likelihood that Judge Alito was the choice. And a high-ranking Republican official told The New York Sun yesterday that Mr. Alito had traveled to Washington over the weekend. The source warned, however, that similar reports circulated about Judge Clement in the hours before Judge Roberts was nominated.

Several sources said that Mr. Bush was prepared to make an announcement yesterday but that a decision to delay until Monday was made so as to not interfere with a ceremony at the Capitol last night honoring the late civil rights hero, Rosa Parks. It appeared likely last night that an announcement would be made this morning. Several Democrats took to the airwaves Sunday in anticipation of an announcement, warning against a controversial pick.

The minority leader of the Senate, Senator Reid, of Nevada, and the ranking Democrat on the Judiciary Committee, Senator Leahy, of Vermont, made a similar plea on Friday in a letter to Mr. Bush. They said the withdrawal of Ms. Miers made it “even more important” that Justice O’Connor be replaced by a “mainstream” nominee rather than an activist who would bring “an ideological agenda” to the court.

The chairman of the Senate Judiciary Committee, Senator Specter, a Republican of Pennsylvania, noted on CNN yesterday that Mr. Bush had not taken his advice by waiting until the end of the Supreme Court session to name a replacement for Justice O’Connor, who has said she wants to retire to take care of her ailing husband.

“Right now, there’s a lot of anxiety,” Mr. Specter said. “When you have Chief Justice Roberts – we don’t know how he’s going to vote on critical issues, the second new nominee, the possibility of a third in the near future, perhaps even more, so that the constitution of the court could be changed on very major constitutional doctrines. But the president seems determined to move ahead, and it’s up to him.”