Chief Justice William H. Rehnquist, who joined the bench a generation ago as its often lone voice of conservative dissent and then steadily steered its turn to the right, died yesterday evening at his home in suburban Virginia. He was 80 and had been undergoing treatments for thyroid cancer since October.

In more than 33 years on the high court, the past 18 as chief justice, Chief Justice Rehnquist was widely credited with leading the revolution that gave broader power to states and local governments. He was one of the court's premier conservatives, consistently supporting school prayer and capital punishment and voting against abortion rights and affirmative action programs.

He also presided over rare historic moments, including the court's central role in the disputed 2000 presidential election and the Senate impeachment trial of President Bill Clinton in 1999 - a moment that gave the public an unprecedented televised view of the chief justice in action, seated at the head of the Senate chamber in his self-designed judicial robe with its distinctive gold strips on each sleeve.

President Bush was informed of Chief Justice Rehnquist's death about 11 p.m., according to Jeanie Mamo, a White House spokeswoman.

"The president and Mrs. Bush are deeply saddened by the passing of Justice Rehnquist. His family is in their thoughts and prayers," she said. The president will make a statement after attending church services this morning, Mamo said.

Senate Majority Leader Bill Frist, a Tennessee Republican, joined other congressional leaders last night in expressing sorrow at the death of the chief justice.

"For over three decades, Chief Justice William Rehnquist served our nation with distinction on the Supreme Court of the United States," Mr. Frist said in a statement released by his office. "He was an inspiration to me to be mindful of our duty to history and our place in preserving the strength of this great nation we serve."

Senate Minority Leader Harry Reid, a Nevada Democrat, said Chief Justice Rehnquist led the federal judiciary "with great dignity and clarity."

Robert Weisberg, professor of law at Stanford Law School, Chief Justice Rehnquist's alma mater, said he will likely be remembered as pushing to more power for the states, less for the federal government, and turning the court away from the Roosevelt's New Deal court, with its expansive interpretation of the power of Congress under the Constitution's "commerce clause."

For that reason, Mr. Weisberg said it's "hard to imagine a case where he ever voted for a defendant in a criminal case," except in a 1995 decision that struck down a federal criminal law on gun possession near a school. Chief Justice Rehnquist voted with those who ruled Congress had overstepped its authority in adopting the law.

David J. Garrow, a legal historian, said, "Even those of us like myself who disagreed with many if not a majority of his opinions unanimously respect and acknowledge how he was one of the most successful chief justices in history. He will in the long run be rated a great or near-great chief justice, having nothing to do with ideology or the formal content of his opinons.

"This really really creates a major issue for the president," said Mr. Garrow, who until recently taught at Emory University and now is at Cambridge University.

Mr. Garrow said it's "highly unlikely" that John Roberts will instead be nominated for chief justice, and he predicted that Alberto Gonzales, the attorney general, is a likely choice.

Chief Justice Rehnquist, who was appointed to the court by President Richard M. Nixon in 1971 and elevated by President Ronald Reagan in 1986, was the second-oldest man ever to serve as chief justice. He also came close to matching the 36-year record for serving on the court, and in recent years, he was the subject of perennial speculation about which of the nine justices might announce retirement plans.

But he defied the rumors and stayed put. When the court opened its term in October last year, he was sitting in the middle seat, firing off questions in cases ranging from the future of the federal sentencing guidelines to the death penalty for juveniles.

Over three decades, Chief Justice Rehnquist carved out a staunchly conservative record. But he also showed moderation at key points - voting to protect free speech, for instance, in the Rev. Jerry Falwell's famous battle against Hustler magazine - and had displayed a gentler tone on issues such as affirmative action and gay rights as the court in recent years has shifted more toward more moderate middle ground.

His sometimes gruff questioning and cutting legal opinions belied what longtime court observers say was a genial personality. Even as the court's top administrator, Chief Justice Rehnquist did not take himself too seriously or revel in the pomp of his position. He hosted an annual Christmas caroling party and liked to make small bets with court workers on everything from sporting events to snowfall amounts.

An avid tennis player, he hired three law clerks each year instead of the now-customary four - the better to round out a decent doubles match.

Harvey Rishikof, an administrative assistant to Chief Justice Rehnquist from 1994 to 1996, said he had a wry sense of humor that often escaped notice.