Chief Justice William H. Rehnquist, who has thyroid cancer, was admitted to Arlington Hospital complaining of a fever Tuesday night, the Supreme Court said yesterday.

Rehnquist, 80, was taken to the hospital by ambulance and spent yesterday resting and undergoing tests, said Kathy Arberg, a court spokeswoman.

Reporters who were camped out in front of Rehnquist's house because of recent rumors that he will retire soon saw court police carrying out the chief justice's cane, a shirt, shoes and a pair of trousers, apparently to take to the hospital. After fielding questions about the unusual movements, the court announced Rehnquist's hospitalization.

Doctors interviewed yesterday said fever-producing infections are common in patients who, like the chief justice, have a surgically made opening in their throats to permit breathing.

The opening, known as a tracheostomy, increases the risk of infection in the trachea, bronchial tubes and lungs.

"It is probably something that could be readily treated and wouldn't require hospitalization for long," said Steven I. Sherman, a thyroid cancer specialist at the University of Texas M.D. Anderson Cancer Center in Houston, who noted that he has no direct knowledge of the chief justice's case.

But the events reignited speculation about how long Rehnquist's health will permit him to remain on the court. If the chief justice were to follow Associate Justice Sandra Day O'Connor into retirement, President Bush would have a chance to name two justices at once -- setting the stage for what could be an epic confirmation struggle in the Senate. Washington is following each development and rumor with frenzied interest.

"Among serious court-watchers and political junkies -- and some of us are at the crossroads of those two -- this is more high drama than we want," said Todd F. Gaziano, director of the Center for Legal & Judicial Studies at the Heritage Foundation. "We're almost at the punch-drunk stage."

Like other conservative activists, Gaziano said he has heard "strong speculation that the White House is waiting for Rehnquist to let them know something before it shows its cards on an O'Connor nomination -- or they know something" already and have held back in deference.

Before O'Connor's announcement July 1, White House officials had signaled that they would move quickly to fill a court vacancy -- which most people at the time expected to be created by the ailing Rehnquist. But Bush has pushed off a decision for two weeks already and many strategists now expect no nominee to be named until July 26 or 27.

That has caused consternation even among some of the advisers closest to the White House. "I don't understand the game plan," said one, who spoke on the condition of anonymity to preserve relations with Bush aides.

Administration officials would not discuss the impact of the chief justice's latest illness or speculate on whether or when he might retire. "It's going to come when it comes," one official said. "If it comes, we'll be ready."

Bush met with senators from both parties on Tuesday and plans to interview candidates in coming days. With White House officials keeping information tight, it was difficult to evaluate where the process is heading.

Some allies of the White House said they think Attorney General Alberto R. Gonzales, a close friend of the president's whom many conservatives have opposed, is less likely to be named.

Some new names are now being floated, according to the White House allies, including former deputy attorney general Larry D. Thompson; Judge Alice M. Batchelder of the U.S. Court of Appeals for the 6th Circuit, based in Cincinnati; and Chief Judge Deanell Reece Tacha of the U.S. Court of Appeals for the 10th Circuit, based in Denver.

Bush said yesterday that he is casting a wide net to include some non-judges, as the senators suggested on Tuesday. "Would I be willing to consider people who had never been a judge? The answer is: You bet," he told reporters after a Cabinet meeting yesterday. "We're considering all kinds of people -- judges, non-judges." He added that he is following first lady Laura Bush's advice to consider appointing a woman to replace O'Connor.

Bush did not seem in a hurry. "I intend to do so in a, you know, in a period of time that will give me time to fully analyze the different candidates and speak to them," he said.

For now, the main impact of Rehnquist's hospitalization is to deepen the mystery surrounding the precise nature of his condition, which the court has never described in detail, but which some outside experts have suggested is a highly aggressive disease, anaplastic thyroid cancer. Only about 10 percent of people with anaplastic cancer survive one year from the time of diagnosis.

The chief justice received his diagnosis of thyroid cancer in October. He spent November in treatment, receiving radiation and chemotherapy. After skipping the court's cases for that month, he resumed work in December. In January, he reemerged for the first time in public, appearing thin and weak as he administered the oath of office to Bush during the president's inauguration.

In the spring, Rehnquist returned to oral arguments at the court, seeming remarkably strong as he peppered lawyers with questions. He spoke with the aid of a valve covering his tracheostomy.

On April 14, Paul W. Ladenson, a thyroid cancer specialist at the Johns Hopkins Medical Institutions and president of the American Thyroid Association, read a letter from Rehnquist to an assembly of about 500 members of the group at the Baltimore Marriott Waterfront hotel.

In the letter, first reported by the New York Times, Rehnquist thanked the organization for helping him resume "some" of his activities. The room erupted in applause, said Gregory Brent, secretary of the association.

In June, Rehnquist was able to make only a 30-minute appearance at a reunion of his former law clerks, far briefer than usual, said several people who attended.

As the court announced its final decisions on June 27, Rehnquist appeared to have weakened again, gasping as he read a few sentences to conclude the session.

But he has since gone to work at the court, having hired three law clerks for the term that begins in October.

The chief justice's response to treatment has caused some physicians to speculate that he may not have had anaplastic thyroid cancer, but an unusually aggressive variant of a more treatable cancer.

"It has to be viewed, with each successive month of survival, that it is less likely that he had that dire diagnosis," Sherman said.

Renaud de Crevoisier of France's Gustave-Roussy Institute, who has extended the lives of some patients with an aggressive combination of surgery, radiation and chemotherapy, said: "Even if it was anaplastic cancer, maybe it was not such an aggressive one at diagnosis. If he had a very aggressive tumor at diagnosis, he would be dead by now."

Staff writers Peter Baker and David Brown contributed to this report.

Supreme Court Chief Justice William H. Rehnquist, who has thyroid cancer, has a surgically made opening in his throat to permit breathing, and doctors said fever-producing infections are common after such procedures.

Rehnquist was admitted to the Virginia Hospital Center in Arlington, where he has been undergoing tests.