Within a day after President Bush taps a Supreme Court nominee, a conservative group with an $18 million budget for the confirmation fight plans to be on the air with a heartwarming ad featuring vintage photos of the candidate to try to cement a sympathetic portrait.

An abortion rights group is poised to shoot a detailed e-mail to 30,000 "rapid responders" who will help generate a barrage of calls to senators and letters to editors saying the landmark Roe v. Wade decision could be in danger. About 800,000 supporters will receive a more general warning and call to arms.

These elaborate opening-day plans are the product of years of preparation and months of drills by groups that see the nomination as the most important social policy battle of the Bush presidency. The plans also reflect the conclusion by both sides that a potentially decisive advantage -- in momentum and public opinion -- can be gained or lost immediately after a White House announcement.

Both sides have prepared hour-by-hour chronologies of Supreme Court fights, ranging from the 73 days from nomination to confirmation for Justice David H. Souter in 1990 to 137 days for Justice Ruth Bader Ginsburg in 1993. In a calculation akin to the "golden hour," in which paramedics race to get a critically ill patient to a hospital, Senate strategists have concluded that the first four to six hours will determine which side is left on the defensive. These minutely detailed strategies are ready to be activated regardless of whom Bush nominates.

The Supreme Court adjourned for the summer on Monday with no retirement announcement, leaving all three branches of government in suspended animation as they await the first vacancy in 11 years. Chief Justice William H. Rehnquist, 80, has thyroid cancer and was absent for large parts of this session. There is also widespread speculation about the intentions of Justice Sandra Day O'Connor, who is 75.

The organization with the $18 million budget is Progress for America, a nonprofit issue advocacy group that spent $45 million on Bush's reelection campaign and has prepared a mammoth dossier on how the opposition has responded to previous Republican nominees, distilled into a "Liberal 10-Step Plan for Judicial Character Assassination." The group says its research found that liberal opponents follow predictable tactics: "Once a nominee is named, immediately announce that the nominee's record 'raises more questions than it answers.' "

Conservatives involved in planning the strategy for a vacancy announcement said they remain haunted by what happened 30 minutes after President Ronald Reagan's 1987 nomination of federal appellate judge Robert H. Bork to succeed Justice Lewis F. Powell Jr. Sen. Edward M. Kennedy (D-Mass.) went to the floor and described "Robert Bork's America" as "a land in which women would be forced into back-alley abortions, blacks would sit at segregated lunch counters."

Republicans now acknowledge they were ill-prepared to counter Kennedy's charges, and the portrayal of Bork as an extremist stuck. After an angry battle that left conservatives with lasting grievances, the Senate voted him down, 58 to 42.

"We responded too late, and it got drowned out," said C. Boyden Gray, who was working in the administration and later became White House counsel to President George H.W. Bush. "We don't want that to happen again. The first hours are when the candidate gets defined."

Now, Gray is chairman of the Committee for Justice, which he founded three years ago to pressure senators to approve the president's nominees. If Rehnquist steps down, the group plans to orchestrate tributes to him for conservatively interpreting the Constitution and promoting religious freedom, saying that this record needs to be extended and enhanced by a like-minded nominee. The group also plans to feed research to conservative bloggers so they can fact-check and counter opponents' claims.

"Our goal is to not let their analysis or spin become defining, and put them on the defensive," said Sean Rushton, spokesman for Committee for Justice.

Republicans have lined up a steady stream of senators to deliver supportive floor speeches. Aides said the party leadership plans to immediately go before cameras with calls for the nomination to be considered in a thoughtful manner that is fair to the nominee, the president and the Senate.

Liberals have made similar preparations. Ralph Neas, director of People for the American Way, surveyed his fifth-floor "war room" in a downtown Washington office building yesterday and said it is essential to be quick off the mark in the round-the-clock news cycle. "Those who frame the debate and define the issues first have a tremendous advantage," he said.

His group is among the largest in a network of liberal organizations whose leaders have worked together for months and will conduct a hasty conference call for last-minute coordination as soon as Bush names a nominee. "Within 15 minutes to an hour, all the leaders will be talking," Neas said.

On the all-but-certain assumption they find Bush's nominee unacceptable, each group will begin e-mailing and telephoning their thousands of members, urging them to call their senators, write letters to newspapers and urge friends to get involved, he said. Neas's war room has about 40 computer workstations and 70 phones, he said, allowing his team to contact thousands of supporters and potential supporters via e-mail and conference calls simultaneously.

NARAL Pro-Choice America is prepared for an all-out battle to thwart a nominee who might overturn Roe v. Wade, which created a legal right to abortion. Spokesman Ted Miller said material warning that a changed court could result in Roe's overturn will be e-mailed to 800,000 activists within minutes of a vacancy announcement. The kits for the 30,000 "rapid responders" will tell them how to recruit volunteers and distribute talking points to friends willing to join the debate.

NARAL President Nancy Keenan noted that her group and many conservatives are joined in an "unholy alliance" on one point: They all want to know precisely how a nominee would vote on Roe v. Wade, despite the usual reluctance of nominees to reveal their views. "We want the senators to ask, and the nominee to answer," she said.

On the other side, the Republican National Committee will join the fray by tapping the network of activists and talk-radio contacts built during last year's presidential campaign. The party also will counter the claims of liberal groups and try to discredit them by drawing attention to their funding sources and partisan boards and staffs.

"It's just like on the campaign," said Brian Jones, the RNC's communications director. "You wouldn't have a John Kerry or John Edwards statement without a response."

People for the American Way is among the liberal groups that will act fast once a nominee is named.