THE usually secretive inner workings of the Central Intelligence Agency's analytical branch came to life this week during a stunning debate over whether CIA director-nominee Robert Gates slanted intelligence reports to suit his own biases and those of his bosses.Suddenly, the nomination appears in trouble. Moderate Democrats who were prepared to support Mr. Gates are backing away from him. At a Monitor breakfast yesterday, Rep. Dave McCurdy (D) of Oklahoma called on Gates to withdraw if he could not prove that he did not skew intelligence. Representative McCurdy does not vote on Gates, but as chairman of the House Intelligence Committee, his view carries sway. "To me slanting intelligence or not allowing dissent is the most damning accusation that you can have," McCurdy said, "because the role of the director of central intelligence is to be a messenger, and the messenger has to be able to deliver bad news as well as good news.... The objectivity of that director is absolutely essential." McCurdy could not characterize how widespread the dissatisfaction was among the ranks of CIA analysts when Gates was both director of intelligence and deputy director of the intelligence community. But, he observed, the CIA is "not just an agency, it's a culture," and for anyone to emerge with criticism is to put oneself at great risk of being blackballed. Supporters of Gates have conceded that the agency's intelligence directorate had become politicized, but that Gates was not to blame. Douglas MacEachin, chief of CIA arms control intelligence, accused Gates's critics of doing exactly what they complain others had done: relying on hearsay and skewing the evidence to fit preconceived notions. Ironically, Gates's travails arose after he seemed to have cleared his highest hurdle: the Iran-contra affair, and what he allegedly knew about it. His immediate admissions of "misjudgments" disarmed Gates's critics on the Senate Select Committee on Intelligence. By the end of the second day of testimony, Sen. Howard Metzenbaum (D) of Ohio, one of Gates's toughest Senate critics, was ruefully telling the media that Gates was likely to be confirmed. Two weeks later, enter the analysts. Some have stepped forward to praise Gates, a career CIA analyst of Soviet affairs, as a brilliant thinker and tough-as-nails bureaucrat. Others have pilloried him for allegedly intentionally overstating the Soviet threat. The latter testimony, and newly declassified documents, caught headlines this week. The burden now lies on Gates's shoulders to refute the charge. One former CIA analyst of Soviet affairs who had served under Gates, Jennifer Glaudemans, testified that his presenting of slanted intelligence on the Soviet Union produced "tragic consequences," such Iran-contra. In documents made public this week, CIA analysts in 1985 had complained in writing that, while working under Deputy Director for Intelligence Robert Gates, their analyses of Soviet-Iranian relations were skewed to exaggerate the Soviet role in Iran in order to support the notion of secret arms sales to Iran. "I believe that the system as it has worked in regard to Iran over the last 18 months has resulted in distorted, uninformed, and in some instances inaccurate information being presented to officials of this government who presumably believed that they were receiving the collective judgment of this agency," wrote Thomas Barksdale, the CIA's top Iran analyst, in late 1986. In particular, CIA analysts testifying against Gates charge, the only acceptable line to follow on Iran in the mid-1980s was that a moderate wing of the Iranian leadership wanted a warming of relations with the United States - and thus, the need to curry favor with arms shipments. One Gates critic who came in for serious criticism himself was Melvin Goodman, a former CIA analyst of Soviet affairs. In his testimony, Mr. Goodman said that in 1985, director of central intelligence William Casey had asked Gates to put together a study on the 1981 assassination attempt on the Pope. Casey had all along believed the Soviets were behind the attempt, and, according to Goodman, Gates's study did not consider evidence that the Soviets were not involved. The title of the study Agca's Attempt to Kill the Pope: The Case for Soviet Involvement has been held up as an example of the study's inherent slant. After Tuesday's damaging testimony, which some Democratic senators say caused them to think twice about supporting Gates - or even to move into opposition, as Sen. Ernest Hollings (D) of South Carolina announced - some Republicans on the Senate committee came back loaded for bear. Sen. Warren Rudman (R) of New Hampshire, a strong Gates backer, turned on his prosecutorial skills as he sought to weaken Goodman's stridently anti-Gates posture.