Activists on the right and left are priming for a battle supreme. If President Bush nominates the first new Supreme Court justice in more than a decade, a fight is expected to break out within hours of an announcement.

Overnight, the Internet will buzz with e-mails, pro and con. Radio and television talk show hosts will jawbone about the testy Senate confirmation battle that's anticipated. Television ads will air for and against Bush's pick. Grass-roots groups will cheer or boo the nominee — with shouting perhaps the loudest in states with senators up for re-election next year.

A vacancy could occur later this month when the court's term closes. Chief Justice William H. Rehnquist (search) is ailing from thyroid cancer. At 85, John Paul Stevens is the oldest justice, and two others are in their 70s.

"The American people ought to prepare themselves to participate in one of the most extensive debates and conversations that's been had in more than a decade about the Supreme Court," said Nan Aron, director of the liberal Alliance for Justice (search), one of two organizations steering a coalition of groups on the left.

In the conservative corner is the Committee for Justice (search). Director Sean Rushton says his group is the "air traffic controller" of the right-of-center campaign to seat a conservative judge in the mode of justices Clarence Thomas or Antonin Scalia. He said many groups on the right say that if Rehnquist is going to step down, they hope Congress could finish the confirmation process before the August recess.

"I think there's a sense that in the past, the left has really made excellent use of the month of August when senators are all back home," Rushton said, recalling President Reagan's 1987 nomination of Robert Bork (search), who after being portrayed as a brilliant jurist and a dangerous extremist, was rejected by the Senate, 58-42. "In Bork's case, liberal groups really drove the dagger in particularly brutally during August."

The Committee for Justice, which has close ties to the White House, was formed three years ago at the request of Sen. Trent Lott of Mississippi, then the majority leader, and the urging of Bush's top political adviser, Karl Rove (search). They wanted to see groups on the right counter long-established ones on the left.

The group holds weekly conference calls with conservative groups, raises money and keeps in touch with powerful players in Washington with a role in the Supreme Court nomination process. Committee for Justice is steered by C. Boyden Gray, the White House counsel to former President George H.W. Bush who helped Thomas through a contentious confirmation amid allegations of sexual harassment.

Gray also is on the board of Progress for America, a group that spent heavily to oppose Sen. John Kerry in last year's election and spent more than $3 million to help Senate Republicans prevent filibusters on judicial nominations.

Rushton insists the left has much more money to block a conservative nomination to the court than the right has to promote one.

"There's not a lot of money on this issue on the right," he said. "Business has given some money, but nobody has stepped forward and said, 'Let me write you a seven-figure check."'

Ralph Neas, who directs the liberal People for the American Way, said left-of-center groups spent an estimated $5 million to try to save the filibuster.

"Having been on the opposite side of Boyden Gray and his special-interest clients, I know how much they can raise," Neas said. "Their pockets are as deep as any pockets in the advocacy world."

Neas and Anon at the Alliance for Justice are assembling troops from a broad coalition of labor, civil rights, environmental and abortion-rights groups, including NARAL Pro-Choice America (search), which has been rallying its forces with call-to-action e-mails.

One sent last week depicts a mock help-wanted ad for a Supreme Court justice. "Narrow-mindedness and interest in turning back the clock on women's rights a plus," the ad said.

Once a vacancy occurs, a "war room" equipped with 50 phones and computers will spring into action at The People for the American Way office, just blocks from the White House.

"If there is a nomination, I'm sure they have their 24-hour plan and their 48-hour plan," Neas said. "Their spokespeople will be prepared, and so will we."

Also in the ring on the right are: Edwin Meese, former attorney general for President Reagan; and Leonard A. Leo, executive vice president of the Federalist Society, which has assembled a list of conservative lawyers and law professors willing to weigh in when the battle begins.

Helping rally the religious right is Jay Sekulow, chief counsel for the American Center for Law and Justice, a nonprofit public interest legal group founded by religious broadcaster Pat Robertson.

The newly formed Judicial Confirmation Network distributes information through other conservative groups, including Focus on the Family, Americans for Tax Reform, Family Research Council and the Americans for Limited Government. The network has operations, manned by paid staff, up and running in Virginia, Maine, Florida, Arkansas, Nebraska and Colorado.

The network, coordinated by Gary Marx, a Bush-Cheney campaign official, and Wendy Long, has also has hired a public relations firm that advised Swift Boat Veterans for Truth, an organization that accused Kerry of inflating his Vietnam War record during last year's presidential campaign.

"We've been saving our quarters," said Long, a former law clerk for Thomas and mother of two who took a leave from her job as a partner in a New York law firm to help coordinate the effort. "We're roughly budgeting a few million for ads for the Supreme Court fight."