WASHINGTON — At the nation’s top spy agency, the ghosts of Iraq are never far away.

One C.I.A. analyst who had helped develop some of the intelligence about Saddam Hussein’s supposed weapons of mass destruction had a breakdown months after the Iraq war began; he had participated in the post-invasion hunt there that found the weapons did not exist. When he eventually was given a new assignment assessing Iran’s nuclear program, he confided a fear to colleagues: that the intelligence community might get it wrong again.

“He felt enormous guilt that he had gotten us into the war,” said one former official who worked with the analyst. “He was afraid it was going to be déjà vu all over again.”

Today, analysts and others at the C.I.A. who are struggling to understand the nuclear ambitions of Iran are keenly aware that the agency’s credibility is again on the line, amid threats of new military interventions. The intelligence debacle on Iraq has deeply influenced the way they do their work, with new safeguards intended to force analysts to be more skeptical in evaluating evidence and more cautious in drawing conclusions.

Former intelligence officials say that this shows appropriate vigilance in dealing with often murky information, while some detractors argue that the agency is not just careful but also overly skittish on Iran, reluctant to be blamed for any findings that might lead the United States to bloodshed.