WASHINGTON – The White House gathered key political operatives at a strategy meeting Friday to prepare for a possible Supreme Court vacancy that officials believe could occur this week, leading to the first high court confirmation battle in a decade, according to Republicans informed about the session.

The meeting – hosted by the White House chief of staff, Andrew Card Jr.; his deputy Karl Rove; and counsel Harriet Miers, was called to ensure that President Bush’s supporters are ready for the high-stakes, high-intensity, high-dollar campaign that would follow a nomination. But some participants later told associates that they were not sure if any justice would retire.

Much of Washington has been anticipating word from Chief Justice Rehnquist on whether he will retire after 19 years as the nation’s top judge. Chief Justice Rehnquist, 80, has thyroid cancer, and many officials, jurists, and activists believe he will step down after the court’s current term ends today. From the White House and Capitol Hill to lobbying groups, both parties spent the weekend mobilizing on that assumption.

Chief Justice Rehnquist’s resignation would presage a struggle of enormous proportions between the two parties and their ideological allies – one that would likely eclipse the recent Senate showdown over lower-court appointments and that could overshadow the rest of Mr. Bush’s domestic agenda for months.

By most accounts, it would rival a presidential campaign, complete with extensive television advertising, mass e-mails, special Internet sites, opposition research, public rallies, and news conferences. Both Democrats and Republicans have been raising money for this moment for years. The president’s allies have promised to bankroll an $18 million public relations blitz, and administration opponents have set up a war room and enlisted veterans of the campaigns of President Clinton and Al Gore to devise strategy.

“This has been such a huge political spectacle that this is not your run-of-the-mill confirmation hearing,” a former Reagan White House chief of staff who shepherded two high court appointments through the Senate for President George H.W. Bush, Ken Duberstein, said.

Since Mr. Clinton’s 1994 appointment of Stephen Breyer, no justice has left the court, the longest period of stability since the 1820s. Although Supreme Court nominations at times have polarized Washington and much of the nation – most notably those of Robert Bork and Clarence Thomas – none has taken place in an era so saturated by 24-hour cable news, e-mail, bloggers, talk radio, and seemingly bottomless financial resources.

If Mr. Bush nominates a like-minded conservative, Chief Justice Rehnquist’s retirement would not put the philosophical balance of the court in play. But it would still generate fireworks because the court is closely divided on many key issues, particularly the Roe v. Wade decision establishing a woman’s right to an abortion. If Mr. Bush picks someone around age 50, as advisers expect, the next chief justice could run the court for three decades.

Conservatives want to ensure that Mr. Bush remains faithful in his selection rather than choosing a moderate who might be easily confirmed by appealing to Senate Democrats. The situation would become even more heated if another justice retires, particularly the centrist-conservative Justice O’Connor, 75, or the liberal Justice Stevens, 85 – a prospect most, but not all, insiders discount.

The White House has been preparing for a nomination for four years and almost certainly would be ready to announce a choice right away. Outside advisers believe the front-runners are U.S. Court of Appeals judges, Michael Luttig of the 4th Circuit, and John Roberts of the D.C. Circuit, both considered strong conservatives. Mr. Bush might also prevail upon his reluctant friend, Attorney General Gonzales, who would be the first Hispanic justice but is seen by some conservatives as unreliable on issues such as abortion and affirmative action.

Other possible candidates include Appeals Court judges, Samuel Alito Jr. of the 3rd Circuit, Michael McConnell of the 10th Circuit, Emilio M. Garza of the 5th Circuit and J. Harvie Wilkinson III of the 4th Circuit. White House advisers doubt Mr. Bush would elevate a current member of the Supreme Court to chief justice.