WASHINGTON -- When religious conservatives rally their troops for the much-anticipated fight over the Supreme Court's next vacancy, they invoke Roe v. Wade. When regulatory lawyer C. Boyden Gray recruits business executives for the battle, he cites Geier v. American Honda Motor Co.

In that 2000 case, Alexis Geier sued the auto maker over injuries suffered in an accident, arguing that the company should have installed airbags, even though federal regulators didn't require them at the time her car had been made. The high court sided with Honda, but only barely, in a 5-4 split. The votes didn't follow stereotypical ideological lines. Chief Justice William H. Rehnquist sided with a majority that flexed federal muscle to protect a big corporation. Fellow conservative Clarence Thomas voted with a minority defending states rights -- in this case, the authority of state courts. If President Bush were to replace the ailing chief justice with a Thomas-like conservative, Honda would have lost, and a new avenue to sue corporations might have opened.

With the high court wrapping up its term Monday, speculation is rampant that a Rehnquist retirement could come soon. Mr. Rehnquist, who has thyroid cancer, hasn't signaled his plans, and his life appointment means he is under no obligation to leave. But even if the chief justice chooses to continue for a time, Washington is bracing for an epic showdown over a Rehnquist successor in the near future.

The spotlight has focused on the religious right and its efforts to leverage its political muscle in reshaping the American legal system. But the other major pillar of the Republican coalition -- business -- has realized that with cases like Geier v. Honda in the balance, it needs to join the fray.

The emerging corporate agenda is different from, and at times contradicts, that of their religious-conservative allies. The Christian right, represented by groups such as the Family Research Council in Washington, has been lobbying the Bush administration to appoint a Supreme Court justice who opposes abortion and gay marriage and favors school prayer and public religious displays. Top business priorities include more protection for intellectual-property rights, more flexibility in clean-air emissions standards, restriction of jury awards and a lenient interpretation of the Sarbanes-Oxley law that imposes new accountability and disclosure requirements on businesses.

Business cases, many concerning the reach of regulation and interaction of state and federal governments, consume a large chunk of the Supreme Court's docket. Now for the first time, the National Association of Manufacturers, which represents big corporations, is creating a committee of executives to screen the business rulings of prospective nominees. The U.S. Chamber of Commerce, which has a broader business constituency, is combing federal rulings and readying a team to analyze a nominee's record as "a liability expander or a liability restrainer."

Business advocates concede that previously they hadn't been as aggressive as social conservatives when it comes to Supreme Court nominations. The complexity of the business issues that come before the high court and worries about alienating Senate allies help explain the difference.

But attitudes are changing, says Stan Anderson, executive vice president of the chamber. "If we're going to be proactive, it may be that you should get involved earlier in the process."

What business wants from the high court sometimes undercuts basic conservative principles. One example has to do with federal authority and states rights. Corporations increasingly have sought protection from unfavorable state laws and court rulings by arguing that federal law "pre-empts," or sets aside, that of the states. This argument could be used to rein in ambitious state attorneys general, such as New York's Eliot Spitzer, who has tried to apply more stringent standards for corporations than those sought by the Securities and Exchange Commission or the Environmental Protection Agency.

Religious conservatives, by contrast, tend to embrace the more traditional conservative position favoring states rights. So they encourage states and municipalities to stretch or go beyond high court precedent on abortion, prayer in public or religious displays. Tony Perkins, president of the Family Research Council and a former Louisiana legislator, says he is well aware that businesses wants national rules that pre-empt the sometimes-conflicting patchwork of state and local regulation. But "that is inconsistent with the predominant judicial philosophy that the president has nominated," he says.

In some cases, the biggest heroes of social conservatives -- Justices Thomas and Antonin Scalia -- have given jitters to corporate lawyers. This often-allied pair has concluded that the Constitution contains nothing that protects business from huge punitive damage awards. In 1995, a court majority threw out a $2 million damage verdict against BMW for failing to disclose that a car had been damaged before sale. Justice Scalia dissented. In a speech earlier this year, he mocked the majority for inventing a nonexistent "Excessive Damages Clause of the Bill of Rights."

The potential for outright conflict between business and religious conservatives is personified by Justice Stephen G. Breyer, a Clinton appointee. Pro-business legal scholars and practitioners say the former law professor and aide to liberal Sen. Edward M. Kennedy has the best understanding of corporate issues of any current member of the court. Justice Breyer wrote the majority opinion favoring Honda in the Geier case.

James Dobson, president of the Colorado-based conservative-advocacy group Focus on the Family, once said Justice Breyer ought to be impeached because he was too sympathetic to gay rights.

Business goals at the high court often don't arrange themselves along neat political lines, says the Chamber of Commerce's Mr. Anderson. "The issue just doesn't square between who is conservative and who is liberal."

Social groups, especially on the right, see judicial appointments as their top priority and are prepared to fight ferociously for them. Conservative activists blame the high court for thwarting their legislative victories in the states and on Capitol Hill.

Businesses traditionally have fretted that waging a protracted nomination fight could endanger other legislative aims and alienate important senators. The Committee for Economic Development, a pro-business think tank, recently held a forum in Washington called "Holding the Center: Depolarizing the Judicial Nomination Process." There, Charles Fried, a Harvard law professor who served as solicitor general during the Reagan administration, urged executives to get involved so "the debate will not be left to Focus on the Family and People For the American Way," a left-leaning activist group.

Of the names thought to be on the White House short list for the next high court opening, nearly all are considered rock solid by religious conservatives. From a business perspective, there is much less certainty.

Two lower-court judges have drawn interest in corporate circles because they represented companies on regulatory matters before going on the federal bench: John Roberts of the Washington, D.C., Circuit Court of Appeals and Michael McConnell of the 10th Circuit Court of Appeals in Denver. Judge McConnell has become best known among those handicapping the court-selection process as an outspoken advocate for overturning the 1973 Roe v. Wade abortion-rights decision.

At the state level, where most major injury-liability cases are decided, business groups have been active in the judicial-selection process for a number of years. Unlike members of the federal bench, many state judges are elected. Businesses have run big-money campaigns to boost sympathetic candidates. The U.S. Chamber of Commerce runs a multimillion-dollar state-judiciary campaign operation that makes contributions and sends out direct mail.

But until now, trade groups like the chamber mostly stayed out of the debates shaping the federal courts. The chamber's practice after a Supreme Court nomination has been to issue a press release endorsing the president's choice and then step aside.

Then in 2002, Mr. Gray formed the Committee for Justice at the behest of then-Senate Majority Leader Trent Lott to help Republicans and the new Bush White House defend any future Supreme Court nominees. Mr. Gray, who was White House counsel for the first President Bush and a veteran of the bloody battle over Justice Thomas's nomination a decade earlier, set the goal of building the broadest possible coalition. One of his targets was the business world, whose deep pockets and effective lobbying machine on regulatory issues could greatly help in any such campaign.

Mr. Gray has received backing from an old ally: John Engler, the former governor of Michigan and new head of the National Association of Manufacturers. (Mr. Engler also is a member of the board of directors of Dow Jones & Co., publisher of this newspaper.)

In appearance, they are quite different: Mr. Gray, a southern, tobacco heir, has an aristocratic air. Mr. Engler is a plain-spoken Midwesterner. They first worked on judges nearly 20 years ago, when Mr. Gray, as White House counsel, tapped Mr. Engler, then the Michigan state Senate leader, to help recruit federal-court nominees. In his three terms as governor, Mr. Engler organized business interests to raise money for judicial campaigns. Mr. Gray traveled to Michigan to help with that effort.

Mr. Engler took the top job at the manufacturers group in 2004, and Mr. Gray soon invited him to step up their partnership. Not long into Mr. Bush's new term, the president gave companies a new incentive to pay attention, when he signed into law a measure moving many class-action cases to the federal courts, where businesses think they will get a fairer hearing.

Mr. Engler began making the rounds in Washington, pitching a new corporate activism on judicial nominations. He informed the offices of the White House counsel and political adviser Karl Rove about his plans. He met privately with Senate Majority Leader Bill Frist and other top Republicans. His message: "This is something we have a big stake in, and we must be involved."

This month, as speculation heightened about Mr. Rehnquist's possible resignation, Mr. Engler and his executive committee approved a creation of an endorsement process for Supreme Court nominees. A new committee of executives will vet any White House nominee based on his or her business rulings.

The NAM committee's findings will be distributed to Capitol Hill and to the arsenal of advocates employed by the association's more than 220 trade-association members. They will also go to--,000 corporations, including Toyota Motor Corp., Emerson and Caterpillar Inc. Those member companies and groups, in turn, have the ability to activate roughly 17 million employees and executives to exert local pressure on wavering senators. Big employers increasingly have tried to mobilize their workers on other political issues.

But business may have only limited impact, at least in the near term, because the NAM committee hasn't vetted the records of prospective nominees on the White House short list. Socially conservative groups have file cabinets full of data on potential nominees that they updated last December when Mr. Rehnquist announced he was undergoing cancer treatment.