As Rudolph W. Giuliani runs for president, his image as a chief executive who steered New York through the disaster of Sept. 11 has become a pillar of his campaign. But one former member of his inner circle keeps surfacing to revisit that history in ways that are unflattering to Giuliani: Jerome M. Hauer, New York City's first emergency management director.

In recent days, Hauer has challenged Giuliani's recollection that he had little role as mayor in placing the city's emergency command center at the ill-fated World Trade Center.

Hauer has also disputed the claim by the Giuliani campaign that the mayor's wife, Judith Giuliani, had coordinated a help center for families after the attack.

And he has contradicted Giuliani's assertions that the city's emergency response was well-coordinated that day, a point he made most notably to the authors of "Grand Illusion," a book that depicts Giuliani's antiterrorism efforts as deeply flawed.

Hauer does not disparage Giuliani's overall effort at emergency preparedness or appear to have actively sought out a role as a Giuliani scold. But he has emerged as one in several settings where his frank, often blunt, answers to questions have offered a rare view inside the often-insular Giuliani administration.

Hauer was once part of the coterie of high school chums, fellow former prosecutors and City Hall aides who remain the nucleus of Giuliani's tight-knit set of advisers. From that perch, he helped Giuliani confront some of New York City's most disquieting predicaments, like the West Nile virus and a potential millennium meltdown.

He emerged from four years of service to Giuliani as one of the country's better-known emergency preparedness experts and a frequent guest on television news programs.

But in recent years, Hauer and Giuliani have had a falling out, though they disagree on just why.

Now from a distance, Hauer offers views of Giuliani's management style, ones that depict him not only as highly competent, and exceptionally hands-on, but also as insensitive and retaliatory at times.

Hauer, for example, recalls a conversation he had with Giuliani in 2001 when he had decided to endorse a Democrat, Mark Green, for New York City mayor over Giuliani's own choice for a successor, Michael R. Bloomberg, a Republican. Hauer said Giuliani, upset, called up to say his disloyalty was unforgivable.

"He was shouting, 'If you do this, you're done, I'm going to end your career,' or something along those lines," Hauer said.

Joseph J. Lhota, a former deputy mayor, remembered the endorsement debate differently, suggesting that Hauer had put politics over principles in a way that "put his whole credibility in question."