WASHINGTON - It has been 10 weeks since then-administrator Sean O'Keefe said he was leaving NASA to take a high-paying university job.

Without a permanent replacement named, lawmakers and experts worry there's no one to lead the sensitive political and public relations efforts necessary to get President Bush's space exploration vision moving.

"NASA should not be in drift," said Sen. Bill Nelson, D-Melbourne.

While there have been spasms of speculation about the Bush administration naming a replacement for O'Keefe, no nominee has been declared. Shuttle veteran and longtime NASA executive Fred Gregory is temporarily at the helm of the 18,000-person agency.

Since O'Keefe announced his departure, the Bush administration appears to have been occupied with other priorities including Cabinet-level nominations, Bush's inauguration, the annual State of the Union speech, a trip to Europe and Russia and more recently the push to restructure Social Security.

Part of the delay is because the administration realizes just how critical the next administrator will be, said Rep. Tom Feeney, R-Oviedo, whose congressional district includes Kennedy Space Center.

"They realize this has become almost like a Cabinet-level selection," Feeney said. "The type of person that can sell the future of NASA the way the president wants requires a more thoughtful selection process. I'm confident that's what's happening."

The National Aeronautics and Space Administration can generate intense public interest; its Web pages got 18 billion hits in 2004, the year the Mars Rovers landed and began exploring the Red Planet.

But the agency administrator does not carry the weight of a secretary of homeland security or health and human services -- both Cabinet-level positions filled since O'Keefe submitted his resignation letter.

Just Friday, Bush nominated Stephen Johnson to become administrator of the Environmental Protection Agency, an independent agency like NASA. Johnson had been serving as EPA acting administrator.

A White House aide said the administration is not dragging its feet on an O'Keefe replacement.

"The president will be putting forth a nomination in a timely manner," said Erin Healy, a White House spokeswoman.

When Bush first took office in 2001, it was 10 months before he named O'Keefe to replace the departing Dan Goldin. Although there has been speculation the White House has offered the job only to be turned down by one or more candidates, there seems to be little truth behind the rumors.

Internet and news media reports recently declared Dan Crippen, the former director of the Congressional Budget Office, was to be nominated for the agency's top job. The claims proved to be nothing more than empty speculation.

"All I know is it's not me," Crippen said. "I didn't interview. I haven't been contacted. I haven't been asked. Nor do I expect to be asked."

Other factors may be contributing to the deliberate pace of the White House search for a new NASA chief.

Bush got burned when homeland security secretary nominee Bernard Kerik withdrew his name from consideration after it was disclosed he had employed an undocumented immigrant as a nanny. The experience raised the bar on all future nominees in the Bush White House where diversions from the approved script are not taken lightly.

Pay could be a factor. The NASA administrator's job pays $162,100, compared with Cabinet secretaries who make $180,100, according to the Office of Personnel Management.

Still, both salaries pale in comparison to what CEOs and top managers demand in the private sector. Not to mention money does not go as far in metro Washington.

O'Keefe is an immediate example. His new job as chancellor of Louisiana State University pays a reported $400,000.

Bob Walker, a former congressman and space policy expert, speculated that it may be getting harder to fill the NASA job for two reasons. First, the job requires a demanding suite of skills, Walker said.

"You need somebody who has some fundamental understanding of what the agency does. You need someone who has the administrative ability to deal with a fairly widespread network. And you need someone with the political skills that can work both inside the administration and with the people on Capitol Hill," Walker said.

Second, there are mandatory background checks, pre-employment financial disclosures and postemployment restrictions that squeeze the pool of willing and qualified candidates.

"The revolving door rules we have . . . makes it real difficult to find people," Walker said.

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