Unlike any presidential science adviser in recent memory, Dr. Marburger immediately made his party affiliation known - when, in answer to a reporter's question, he declared himself a lifelong Democrat. Considering that Dr. Marburger would be joining a Republican administration as one of Mr. Bush's senior advisers, the declaration has raised new questions about what role science will play in the administration.

"Quite candidly I'm a little surprised," said Dr. John Gibbons, the science adviser to President Bill Clinton, who held a number of posts in Republican and Democratic administrations but, he says, never formally declared himself a Democrat. He said he was not sure whether Dr. Marburger's avowal showed "a little political naiveté."

Dr. D. Allan Bromley, who was science adviser to President Bush's father, also questioned the decision to make a political declaration, saying, "I certainly don't think it was necessary in any sense."

But politics should ultimately be unimportant, he said, because Mr. Marburger's influence will rest on his ability to deliver unbiased scientific advice and on his personal relationship with the president.

"While you hold the position, you simply do not have an agenda of your own," Dr. Bromley said.

Dr. Bromley, who said he was involved in the search for candidates, confirmed that several potential nominees had taken themselves out of contention.

Many scientists have criticized the administration for waiting five months to name a science adviser, saying that its statements on issues like global warming and missile defense betray a lack of technical sophistication.

Because the science adviser also directs the Office of Science and Technology Policy, Dr. Marburger must be confirmed by the Senate, something that may not take place until fall.

As is customary, Dr. Marburger has stopped granting interviews until after the confirmation hearings. But through a Brookhaven spokeswoman, Karen McNulty Walsh, Dr. Marburger said he was indeed a lifelong Democrat, though not politically active. Ms. McNulty Walsh said Dr. Marburger added that he had worked productively with elected officials from each party at all levels of government.

Born on Feb. 8, 1941, in Staten Island, John Harmen Marburger III graduated
from Princeton and received a doctorate in applied physics from Stanford in 1967. His research focused on the interaction of intense light with matter.

After more than a decade of teaching and research at the University of Southern California, he headed back east to the State University of New York at Stony Brook, serving as its president from 1980 to 1994. During his tenure there and at Brookhaven, he garnered respect from across the political spectrum for his handling of contentious issues.

"As an adviser to the president he is absolutely perfect," said Dr. Robert McGrath, a physicist, who is provost and executive vice president for academic affairs at SUNY-Stony Brook, and who is also the university's vice president for Brookhaven affairs. "I just am in awe of what he's been able to do with this laboratory."

The laboratory has already begun a search for a new director.

While that sort of praise may be expected from Dr. Marburger's close colleagues, it is largely echoed in much less likely quarters - the environmental organizations that long had adversarial relationships with the laboratory before Dr. Marburger became its director in 1998.

Those relationships arose from pollution problems at the lab, some of them decades old. They included leakage of chemical waste and small amounts of radioactive tritium from part of a nuclear reactor used for research.

Dr. Marburger set up a permanent advisory council to make the concerns of the surrounding community on Long Island known to the lab's managers, met with local environmental groups and worked to accelerate the schedule for cleaning up pollution at the lab. Eventually, he supervised the permanent shutdown of the reactor after it was ordered by Bill Richardson, then the secretary of energy, late in 1999.

"He's lived up to the enormously tough challenge that he faced there," said James Tripp, general counsel of the Environmental Defense Fund.

Scott Cullen, legal counsel for Standing for Truth About Radiation, a Long Island environmental group, said that while much work remained to be done in eliminating the contamination, much of the distrust had dissipated. "To Dr. Marburger's credit, what he did at the laboratory was change the way that the lab interacted with the Long Island public," Mr. Cullen said.

Dr. Marburger also presided over a scientific comeback of sorts for Brookhaven, where a giant particle accelerator called the Relativistic Heavy Ion Collider recently produced the densest matter ever created in a laboratory. The achievement is a step toward understanding the Big Bang explosion in which the universe is thought to have been born.

Cleanup money for Brookhaven, increased last year, was sharply cut under the Bush budget, although recent efforts have been made to restore the cuts. Dr. Marburger's record at the laboratory contains broad hints that he may not be entirely in tune with an administration whose environmental stance has been sharply criticized.

President Bush cited uncertainties in the science of climate research as one reason not to join the Kyoto accord on global warming. Dr. Marburger has not spoken publicly about that issue, though a colleague, Dr. Robert de Zafra, a physicist and environmental researcher at SUNY- Stony Brook, said, "Most certainly he is a concerned environmental advocate."

In other areas, like some aspects of energy production, there may be no gap at all. Dr. Marburger, who was appointed by Gov. Mario M. Cuomo in 1983 to lead a fact-finding commission on the troubled Shoreham nuclear reactor on Long Island, is likely to agree with the Bush administration's decision to promote nuclear power as an element of the nation's energy future.

"Jack would classify himself as generally being pro-nuclear," said Dr. John Bjorkholm, a principal scientist at Intel and a longtime friend.

But the tardiness of the nomination could present its own problems for Dr. Marburger. The Bush administration's decision on whether to allow federal financing of research involving human fetal tissue and fertilized eggs - research that could be useful in treating diseases like diabetes but is opposed by some groups - could come this month, long before confirmation hearings.

And if the hearings drag very far into the fall, the administration's proposed budget for 2003 could already be too far along for Dr. Marburger to influence it very much, said Dr. Neal Lane, a physicist who served as science adviser to Mr. Clinton in his second term.

"It's clearly a disadvantage for Jack Marburger coming in late," Dr. Lane said. "I certainly think the community, all of us, should not have unrealistic expectations."

Still, if Dr. Marburger develops a strong relationship with the president and other senior advisers, his voice will eventually be heard, Dr. Lane said.

A White House official said Mr. Marburger's party affiliation was unimportant.

Anne Womack, a White House spokeswoman, said, "The White House has conducted a thorough search for a science and technology adviser, and we feel we've found the best candidate."