It is axiomatic of presidential politics that while many people are concerned about the future of the Supreme Court, the issue mainly influences narrow groups of voters at either end of the political spectrum, and then only by intensifying preferences, Democratic or Republican, they already have.

Both President Bush and Sen. John F. Kerry (D-Mass.) have campaigned as if they accepted that view in 2004. Each has limited his remarks on the court to carefully phrased messages aimed at reassuring his core followers without inflaming his opponent's.

But with the court's announcement Monday that Chief Justice William H. Rehnquist, 80, is suffering from thyroid cancer, the wider public is seeing more news about the prospect of change in the justices' ranks than at any other time in the campaign -- and the presidential candidates' positions on judicial nominations have been thrust into the spotlight.

The current nine justices have been together since 1994, the longest period without turnover at the court since the 1820s. With the court sharply divided between liberals and conservatives on such key issues as affirmative action, abortion rights, states' rights and gay rights, the next nomination to a life appointment as a justice will probably be the focus of intense political combat when it comes before the Senate.

"What we've been saying is that the Nov. 2 election will determine the law of the land for several decades," said Ralph G. Neas, president of the liberal organization People for the American Way.

Indirectly, Bush and Kerry have already clashed over judicial nominations over the past four years. Bush has sent the Senate the names of conservative nominees for federal appellate judgeships. Senate Democrats, with Kerry's support, have blocked them, citing ideology and other factors.

In 2004, the most direct exchange on the issue came during the second presidential debate, on Oct. 8, in response to a question from an audience member.

Bush said, as he has before, that he would put "strict constructionists" on the court. "We've got plenty of lawmakers in Washington, D.C. Legislators make law; judges interpret the Constitution," Bush said.

In a clear appeal to his conservative base, the president said that he would not elevate any judge who would have supported the ruling of a federal appeals court, later overturned by the Supreme Court, that barred the phrase "under God" in the Pledge of Allegiance as recited by schoolchildren.

Somewhat more obscurely, he added that he would not appoint jurists who approve of the Dred Scott decision, a long-discredited 1857 ruling in which the Supreme Court denied citizenship to all black people, free and enslaved. The reference was one that most abortion opponents would have recognized as a signal of disapproval for Roe v. Wade, the court's 1973 decision recognizing a constitutional right to choose abortion.

"It's not unusual for speakers, when they are talking about the life issue, to compare Roe to Dred Scott, because both took a whole class of individuals and said that they are not persons," said Gary Bauer, president of the antiabortion Campaign for Working Families.

Challenged at the third and final debate on Oct. 13 by moderator Bob Schieffer to say whether he supported repeal of Roe v. Wade, Bush replied that he would have no "litmus test" for judicial appointments.

Kerry also appealed to his base on the issue, taking a jab at Bush for his remark during the 2000 campaign that he wanted justices in the mold of Supreme Court conservatives Antonin Scalia and Clarence Thomas -- justices so widely loathed on the left that Democrats recently sent out a mass mailing urging donors to help elect a Democratic Senate lest Republicans confirm "Chief Justice Scalia."

Kerry also flatly stated his support for judges who would uphold Roe v. Wade.

"I'm not going to appoint a judge to the court who's going to undo a constitutional right, whether it's the First Amendment or the Fifth Amendment or some other right that's given under our courts today, or under the Constitution," Kerry said at the third debate. "And I believe that the right of choice is a constitutional right."

The main non-ideological factor in the Supreme Court equation may be ethnicity. For both parties, naming the first Hispanic justice could be a way to curry favor with Hispanic voters.

For Bush, however, this has grown slightly more difficult, according to analysts on both sides of the partisan divide.

White House counsel Alberto R. Gonzales was once thought to be a near-certain pick, but his involvement with controversial administration policies on terrorism detainees may have hurt his chances.

The president tried to appoint Washington lawyer Miguel A. Estrada to the federal appeals court, in an apparent bid to groom him for the high court. But Estrada withdrew amid a Democratic filibuster.

Some Republicans still back Estrada as a dark horse for the Supreme Court, along with federal appeals Judge Emilio Garza.

A President Kerry could turn to federal appeals court judge Sonia Sotomayor. Democrats increasingly speak of a different kind of Supreme Court first, in the form of a nomination by Kerry of David S. Tatel, a federal appeals court judge who is blind and would therefore become the first disabled justice.

If Rehnquist's seat is indeed the first to come open, each party would also have the option of defusing a possible Senate battle by elevating Sandra Day O'Connor, a popular centrist, as the first woman chief justice in tandem with an associate justice nomination.