Randall Kennedy is the Michael R. Klein Professor of Law at Harvard Law School.

‘Thanks to their common goals and trajectories and calendars,” David Margolick observes, Martin Luther King Jr. and Robert F. Kennedy are linked in the popular mind “as no other black man and white man in the history of civil rights have ever been.” King was the most important leader of the black protest movement that, between 1954 and 1968, uprooted de jure racial segregation and put many forms of racial discrimination on the defensive. The Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Open Housing Act of 1968 all derive, directly and indirectly, from King’s inspired rhetoric and much-publicized sacrifice. He was assassinated on April 4, 1968. Kennedy was the director of his older brother John F. Kennedy’s 1960 presidential campaign, served as attorney general of the United States, won election to represent New York in the Senate and sought the presidency before being mortally wounded by an assassin on June 5, 1968. King was 39 when he died; Kennedy was 42.

Because King and Kennedy challenged racism, railed against poverty, repudiated the Vietnam War and were surrounded by publicity that made them beloved and hated, people assume that they were celebrity buddies or, even more than that, close friends. In his book “The Promise and the Dream: The Untold Story of Martin Luther King, Jr. and Robert F. Kennedy,” Margolick shows, however, that that assumption misconstrues their relationship. What he views as their “untold story” is that they were never close. They were intermittent allies but never friends. They spoke infrequently. Almost never socialized together. Seldom did they candidly share their thinking with one another. According to Margolick: “Theirs was an uneven relationship, and for King, a slightly degrading one: he was the black man invariably asking for things, and Kennedy the white man doling them out. . . . King was the one to say ‘please’ and ‘thank you.’ ”

Margolick is a shrewd pointillist with a keen eye for the telling detail, the revealing scene and the memorable quotation. He recalls King losing his racial innocence at 6 when the mother of a white boy explained that her son was “getting too big to play with a nigger anymore.” He notes that a group of whites in Cartersville, Ga., sent a cash contribution to the deranged black woman who stabbed King nearly to death in Harlem in 1958. He recollects the effort by the powerful Louisiana bigot Leander Perez to create “reverse Freedom Rides” in which segregationists would pay impoverished black Southerners to move to the North, including, in particular, Hyannis, Mass., the Kennedys’ stomping ground. He recounts Dick Gregory acidly joking that the most dangerous part of the mission for any black astronaut was travelling through the South to reach Florida’s Cape Canaveral. He points out that while King was arrested 29 times between 1955 and 1967, Kennedy got to be attorney general at 36 with little legal experience. Margolick unearths a statement by the black Olympian Rafer Johnson that Kennedy was “as much a Negro as Adam Clayton Powell . . . Ralph Bunche . . . or Joe Louis.” He notes that when Coretta King received an anonymous mailing containing a recording of her husband’s extramarital sexual exertions — a recording made by J. Edgar Hoover’s apparatchiks — she innocently sent it to the FBI for investigation. He points out that on the Sunday after his murder, King had planned to preach a sermon titled “Why America May Go to Hell.” He quotes Hoover saying that “everyone knows that Negros’ brains are twenty percent smaller than white people’s.”

Although Margolick clearly admires both King and Kennedy, his commendable urge to create a realistic, intimate portrait of the two prompts him to surface actions and statements that will make devotees wince. Taunting a diplomat who planned to attend the famous March on Washington in August 1963, the rally at which King delivered his iconic “I Have a Dream” address, RFK is quoted as saying, “So you’re down here for that old black fairy’s anti-Kennedy demonstration?” — an allusion to the march’s principal organizer, Bayard Rustin, who was then a closeted homosexual. When the diplomat then mentioned King, Kennedy retorted: “He’s not a serious person. If the country knew what we know about King’s goings-on, he’d be finished.” The “goings-on” included, among other things, sexual romps that the FBI recorded pursuant to surveillance that Kennedy, as attorney general, had authorized. Later, in the wake of John F. Kennedy’s assassination, FBI eavesdropping captured King jokingly remarking that sex was what Jacqueline Kennedy would now miss most about the murdered president.

“The Promise and the Dream,” by David Margolick (RosettaBooks)

“It’s hard to imagine,” Margolick comments, “that what the FBI characterized as ‘King’s vilification of the late President and his wife’ did not influence Robert Kennedy’s attitude toward Martin Luther King.”

Impressive in certain ways, “The Promise and the Dream” is deficient in others. With a book of 400 pages, by a serious journalist grappling with significant, contentious issues, a reader expects a deeper, more comprehensive treatment than Margolick sometimes delivers. He notes that when Bobby Kennedy applied to Harvard Law School, his father enlisted the support of James M. Landis, who had succeeded the elder Kennedy as chairman of the Securities and Exchange Commission and became a professor and eventually dean of the law school. In a letter of recommendation to the admissions committee, Landis wrote: “I realize, of course, that his academic record at Harvard [College], is none too impressive. But some men only reveal capacities for work and achievement when they hit the impact of a professional school.” Well, what was Kennedy’s collegiate record? And what was Harvard Law School’s response to his application? He attended the University of Virginia Law School. Did he prefer it? Or was he rejected by Harvard? Margolick leaves these questions unanswered.

Attorney General Kennedy’s authorization to put King under intense FBI surveillance — his phones were tapped and his hotel rooms bugged, he was followed, and informants were inserted into his inner circle — was a key decision. What was its legal basis? The 1976 Senate report that detailed FBI abuses concluded that “high officials of the Executive Branch must share responsibility for the FBI’s efforts against Dr. King.” Margolick adds that “by failing to keep tabs on — and to stop — what the FBI was up to . . . Kennedy inadvertently aided Hoover’s campaign.” But why does Margolick suppose that Kennedy was unaware of the extent to which Hoover was hounding King? If he was unaware, did that constitute gross negligence? Margolick’s discussion of this profoundly troubling episode is all too superficial.

Margolick brings to the center of his narrative Stanley Levison, a former communist whose close affiliation with King served as the main formal predicate for subjecting the latter to FBI surveillance. The Levison-King relationship, Margolick remarks, “is surely one of the greatest cross-racial collaborations and friendships in the history of the civil rights movement.” Yet, according to Margolick, Levison ridiculed King’s writing and described him as “poorly read.” Margolick does not expressly refute Levison. Rather, he suggests that his derisive assessment stemmed from racial bias: “Levison was not above some of the standard prejudices of the day, even with King.” But how is it that a white man whose racism presumably led him to derogate King’s intellectual stature could become, in Margolick’s estimation, “King’s most indispensable adviser, as well as his chief strategist, ghostwriter, fund-raiser, donor, financial counselor, book agent, cheerleader, muse, sage, and friend”?

Trying to explain the inability of King and Kennedy to transcend their alienation, Margolick contends that “the racial and cultural divide between them had simply been too broad.” But that explanation is inadequate given the closeness of the friendship between King and Levison. A racial and cultural gulf also separated them — yet they bonded. Why not Kennedy and King? Were either or both of them too vain? Did their intuitive knowledge of each other counsel protective distance? Was their story a tale of two guys confined to opposite sides — one on the outside looking in, the other on the inside looking out? Perhaps their knowledge of their betrayals of one another was too much of a burden to overcome — a theory that Margolick briefly floats but inadequately pursues.

Friendship arises from a mysterious alchemy. No one can reasonably expect its absence or presence to be fully explained. It is not too much to expect, however, a more rigorous effort than what one receives in “The Promise and the Dream.”

The Promise and the Dream
The Untold Story of Martin Luther King, Jr. and Robert F. Kennedy

By David Margolick

Rosetta. 400 pp. $30