IN THE PREFACE to her study of Jimmy Carter, Betty Glad, a political scientist at the University of Ilinois, says that she finds congenial the psychoanalytical approach to biography. Psychohistory's reputation is dim these days, largely becaus its practitioners have often claimed conceptural breakthroughs on the basis of trivial evidence and dubious logic. So one approaches the bulk of this book with misgivings. Are we in for 500 pages of psychological reductionism, with America's policy toward Iran traced ultimately to the president's toilet training?

At least for the first 475 pages, the answer, mercifully, is no. In that span (beginning with a first chapter titled, inevitably, "Roots"), we get not psychoanalysis, but standard biography, taking Carter's life story all the way through the 1980 presidential primaries. Glad covers now-familiar territory: the small town boyhood, the Navy career, the return to Plains, service in the Georgia legislature, the unsuccessul run for governor followed by the successful one, the long-shot try for the presidency. And although the author inteviewed dozens of people who know Carter, although she consulted reams of public documents, although her book claims somewhat petulantly to be "the only thorough and accurate accunt," the narrative does not alter significantly the general outline of the story already told by James Wooten, Jules Witcover, Elizabeth Drew, and Haynes Johnson.

Glad spends a lot of time correcting the factual record, much of which has been smudged and fudged by Carter himself, especially in Why Not the Best ? Many points are small ones: Carter finished 60th, not 59th, in his Annapolis class; his father probably never made it to lieutenant in World War 1. Glad dots every "i" and crosses every "t", creating, in her determination to be thorough, vast stretches of arid prose -- especially in the lengthy discussions of the 1976 campaign and Carter's presidency -- informed by no explicit theory.

As the points accumulate, however, and as Glad moves from minor issues to major ones, such as Carter's governmental reorganization plans and his civil rights record, the pattern of Carter's self-promotion emerges more clearly than ever before. Glad is espcially good at describing Carter's political style and tactics; her discussions of these subjects stand out like oases in the desert. Carter has always presented himself, she says, as an "extraordinary, ordinary man." As a political candidate, he has avoided ideological labels; his choreography on specific issues has been intended to let him put his best foot forward toward as many different groups as possible. But he seems most comfortable when his own character, not a platform or set of issues, is the campaign's focal point. And he has a mutitude of selves -- "I'm a farmer, a businessman, a Christian" -- that voters can buy off the rack.

As candidate and officeholder, Carter is a "stylistic populist," but he always keeps his lines open to busines and other established interest groups, and he perpetually assesses and reassesses the forces affecting his programs. There's nothing unique to Carter in such behavior, Glad says, except the zeal with which he commits himself to it. His governorship, marked by zigging and zagging, backing and filling, presaged his presidency. He has no real goals beyond simply being president, so he is suersensitive to political pressures that might affect that ambition. In short, Glad's Jimmy Carter, with all his intelligence, personal charm and physical endurance, is a Southern Sammy Glick.

So far, an unstartling, if unattractive, portrait. But in the last 30 pages (labeled "Interpretations"), Glad tries to explain what makes Jimmy run. And she goes overboard. Carter, she says (following psychoanalyst Karen Horney's typology), has an "expansionist (subtype: narcissistic) personality." Such people, loved only conditionally (when they were "good") as children, have "highly idealized images of themselves with which they identify and which they love" -- images often partially realistic, but unrealistic enough to make them lose touch with their own darker urges and detach themselves from people perceived as "different from, rather than extensions of" themselves. Carter, of course, goes to exceptinal lengths to find extensions of himself. For example, he told an audience that when he went last May to meet the families of those killed in the unsuccessful Iranian hostage rescue mission, he had worried beforehand about the encounter. i"But in every instance, they reached their arms out for me and we embraced each other, and I could feel that their concern was about me, not about them."

When facing difficult problems, this personality, according to Glad, takes refuge in symbolic or supeficial solutions. He seldom learns from mistakes, because he can rarely admit making a serious one. A second Carter administration, one infers, would closely resemble the first.

One can agree with Glad's observations about Carter's style and tactics without buying her whole psychological bill of goods. Her assertions about the "compulsiveness" of his behavior are essentially unprovable, at least until someone actually gets Carter on the couch. Her research included virtually no direct contact with Carter himself and very little with his closest associates. So, like the psychiatrists who took on Barry Goldwater in 1964, she is in a poor position to plumb conscious or unconscious motivation.

Glad dismisses out of hand the most obvious alternate explanation of Carter's behavior: that he is not a compulsive neurotic, but a cynical manipulator. Indeed, she makes her particular psychological interpretation bear virtually the entire explanatory burden for Carter's rise, while his current difficulties, too, "to a great extent, are of his own making." External factors, such as the rise of the "special interest state," or the unusual "temper of the times" that made voters in the aftermath of Vietnam and Watergate receptive to a campaign about character but still distrustful of government, are almost completely subordinated to internal, psychological ones. gShe even ignores her own earlier, sensible analysis of how the media's own internal dynamics contributed to Carter's successes, then helped to hamstring him.

In sum, the only force that seems to matter in this book, the only theme uniting its disparate parts, is Carterhs overweening inner drive. Even when we discount Glad's psychoanalytical over-kill, he emerges as the ultimate overachiever, a hyperthyroid Horatio Alger, yet withal, a hollow man. How simple and convenient it would be if we could really lay all our troubles to the discorder in his psyche.