Hauer said he ended up in something of a feud with the police commissioner at the time, Howard Safir, which came to a head in 1998 when, he said, he offered to help both departments prepare for a chemical disaster drill.

Police officials declined help, Hauer said, but then sent detectives to follow him and photograph his meeting with fire officials. During a subsequent meeting with the mayor, Safir held up the photographs, Hauer said, as triumphant evidence that Hauer favored the Fire Department.

"Any man worth his salt would have been outraged that the Police Department followed one of his closest commissioners," Hauer said. "It was disgraceful."

But Hauer said that when he complained to Giuliani, all he got was a blank stare.

Lhota, speaking for the campaign, said he was unaware of such an incident. Safir did not return a call for comment.

Hauer left his city job in 2000. A year later, Giuliani called him back into service after the terror attacks. He was assigned to help prepare for possible biological or chemical attacks and to help set up an assistance center for victims' families.

Giuliani's wife, Judith, who was then his companion, also had a role in setting up the center. But last week Hauer told New York magazine that the campaign's depiction of her role was "simply a lie."

The campaign's Web site said that Mrs. Giuliani had "coordinated the efforts at the Family Assistance Center on Pier 94."

Indeed, others were at least equally involved in that effort. Rosemary O'Keefe, who was then director of the Community Assistance Unit, said that Mrs. Giuliani had helped during the first two days at the pier.

"Judith was a very important part in the very beginning," O'Keefe said in an interview. "I ran it 20 hours a day from that point forward."

Michael McKeon, a Giuliani campaign spokesman, said the campaign never meant to suggest that Mrs. Giuliani played a singular role in coordinating the center, only that she had helped set it up. He said the language on the Web site had been adjusted.

Mrs. Giuliani, McKeon said, is "the first one to give credit to other people."

Hauer, McKeon said, is just bitter.

Siegel said that what is indeed singular is the role Hauer has now assumed, that of a high-ranking Giuliani insider who is now an outsider with pointed opinions on a central topic of the presidential campaign.

"To me, it's unfortunate," Siegel said, "that two people who did so much to prepare the city had a falling out."