As messianic causes go, this one was a little fuzzy. Real-estate discrimination in Chicago in 1966 was a tough and floating target. It wasn’t enshrined in law, but was established by thousands of individual decisions made by brokers and landlords not to rent or loan, by slumlords and city inspectors not to fix, and by political leaders not to care. King staged non-violent protests at the doors of suburban real-estate agencies and savings and loan associations, drawing large white counter-protests incited by such malicious actors as the American Nazi Party. He held meetings with gang leaders, midnight church basement disquisitions with cross-legged members of the Cobras and Roman Saints on the theology and politics of non-violence, and briefly took up residence in a slum. And King went on national television, drawing skepticism from sympathetic network anchors when he told them and the country that racism in Chicago was more pernicious than its formalized, Southern form, and that the problems that trapped blacks in poverty in the North were the nation’s most compelling moral crisis.

In the end, King got outflanked by Chicago mayor Richard Daley. Just as the civil rights leader arrived to set up camp, Daley announced that the city’s workers would raze a thousand slum buildings in six months, and pour far more money into anti-poverty programs in the city’s ghettos. Daley was true to his word, and his police kept King safe from counter-protesters. But Daley also held his ground, insisting just as vehemently that he would not alienate his white constituents by taking legislative measures to pry open middle-class white neighborhoods to blacks, calling King a troublemaker, and asking him to leave.

King had been, in the South, a genius of protest theatrics, but here he had mismanaged and misunderstood things, leaving the theatrics blurred: Weren’t things for blacks in the North on the whole pretty good? And who or what was King attacking, anyway? Wasn’t Daley more or less a liberal, too, and wasn’t he giving King more or less what he wanted? And if Chicago’s blacks really wanted or needed King around, why was the city’s most prominent pastor, the Daley ally Rev. J.H. Jackson, telling the Southern civil rights leader to beat it? King couldn’t keep the Chicago street gangs to their promise of nonviolence, giving Daley cover to call him an outside agitator and summon the National Guard. He couldn’t draw the funding for this project (particularly after Israel’s success in the Six-Day War gave the wealthy New York Jews who had largely bankrolled King another attractive philanthropy) that he had for his Southern campaigns. He couldn’t figure out how to manage Daley, and he couldn’t get the world to care. Eventually, in 1971, SCLC closed down Operation Breadbasket, the project that the Chicago cause had morphed into, without having won a single real victory.

The failure marked the problem of King’s later years, a difficulty in making nonviolent tactics work with allies less unified than the right-to-vote-seeking Southern sharecroppers and against an enemy less obviously pernicious than Bull Connor. But it also described the signal problem of liberal politicians for the next 40 years: How to generate the same moral righteousness and authority that had animated the Civil Rights movement against more subtle problems and actors–poverty, the ghetto, health care, and social mobility. The end of King’s public saintedness marked the beginning of the angst of modern liberalism. Fittingly, by the time Operation Breadbasket was shut down, it was being run by a young Chicago preacher named Jesse Jackson.

The white, Southern journalist Taylor Branch (a Washington Monthly contributing editor) has just finished the last volume of his stunning, exhaustive three-part history of the Civil Rights movement, America in the King Years, which he has been working on for a quarter of a century. The series has already won him the Pulitzer Prize for history and earned him two bestsellers. This last volume, At Canaan’s Edge, includes the Chicago episode and covers the years 1965-1968. It is the most difficult and downbeat of the three volumes because of this material; it also might be the best.

At Canaan’s Edge is a tick-tock history of several different, interwoven stories as they evolved through these three years. The main ones are the fight of the remnants of the old, voters-rights coalition to register African-Americans in Lowndes County, Alabama; the ever-changing conversations within the White House about how to manage the politics of the civil rights movement, which had Lyndon B. Johnson supporting and winning votes for landmark voting rights and anti-poverty bills, before growing angry with King’s perceived disloyalty and backing away from him; and the back-and-forth in the rump Civil Rights establishment around King about what its next move should be, its awkward and failed attempts to articulate a compelling moral case either for a massive initiative against black poverty and discrimination in the North or, later, against the Vietnam War.

Branch’s book is strictly chronological, and so he dips into each of these stories for a couple of pages, then into another, so that he often covers what was happening in all three during the course of a signal day. It sounds jagged, and occasionally the book reads like one of those VH1 documentaries on the sixties, ping-ponging between a Vietnam protester setting himself on fire outside the White House, Stokely Carmichael’s car chase with the Mississippi Klan, and what Lady Bird ate for breakfast that morning. But mostly, Branch’s style lends the book the overwhelming authority of explained motivation. When Johnson chastens George Wallace, or a King speech is more critical of America’s Vietnam policy than anyone expected, the reader understands why; he’s been with these characters for a couple of years, hearing nearly everything they hear, and watching their subtle, often internal political twists and turns.

The characters, after all, are the thing. There’s an eternal battle between academics and journalists in the writing of history, with the scholars emphasizing long arcs of historic force and the hacks stressing the agency of particular figures–a take that has the advantage of making more interesting copy; by my count, Branch’s journalistic history contains at least four stand-ins for Hamlet. One of Branch’s greatest accomplishments and contributions has been to master the complicated characters of the Civil Rights movement, not just King, Johnson, and Carmichael, but lesser figures, too, the liberal New York lawyer Stanley Levison, the FBI man Deke Deloach.

Here is Branch, for instance, summing up the difference between the two presidents King had to deal with: “Whereas Kennedy had charmed King while keeping him at a safe distance, harping in private on the political dangers of alleged subversives in the civil rights movement, Johnson in the White House was intensely personal but unpredictable–treating King variously to a Texas bear hug of shared dreams or a towering, wounded snit.” These are the kinds of distinctions on which history, in delicate moments, can turn.

Branch’s great character is King. One of the questions that still lingers around King, in African-American Studies departments and the more wistful districts of the letters page of The Nation, is whether the history of race relations in the country might have turned out differently if King had survived. Would the radical takeover of the race movement have been forestalled, the left’s moral momentum preserved? Branch doesn’t take on the question directly, but it’s hard to read his comprehensive history and not come to the conclusion that King’s survival probably wouldn’t have greatly changed the course of the country’s racial and political history.

The chronicle Branch gives of the last two years of King’s life is one of a succession of thrashing failures. King couldn’t gin up any popular momentum for the Northern anti-poverty crusade. His tiptoeing, then thundering entry into international relations–in his condemnation of the Vietnam War and support for Israel in the Six-Day War–made him look nave and foolish. His championing of the trash collectors’ strike in Memphis made him look like just another liberal, and a loser, too. And his attempts to manage the emerging radical core of Huey Newton and H. Rap Brown just made him look out-of-touch and ineffective, a kindly but irrelevant grandpa.

None of this, in Branch’s elegant telling, impeaches the nobility of King’s basic imagination, or his undertaking. But it does suggest that there is something tenuous and circumstantial about revolutions. King was just as right when he preached against the problems of the black slum or the repressive working conditions visited upon trash collectors as he was when he summoned a great moral awakening to confront the white Southern forces that kept blacks from voting. But the conflict between evil and good was not nearly so evident. Reading about King’s frustrated efforts, you can see where it’s headed. In hindsight, we anticipate the liberal politics that will mobilize behind the failed assumption that the country will invest in the condition of women or workers or the environment with the same moral vigor that led to the successes of King’s civil rights movements.

Then, of course, there were the white people. Branch very deftly documents the ways in which the careers of an entire generation of conservative politicians depended upon managing the rhetoric of racial backlash. Here, for example, is Ronald Reagan’s voice playing over an ominous film of riots in a commercial for his 1966 gubernatorial campaign: “Every day the jungle draws a little closer…. Our city streets are jungle paths after dark.” And Branch notes that the man who would become Reagan’s presidential successor, then-Houston congressman George H.W. Bush, gave a 1968 speech criticizing “miscellaneous purchases under the federal anti-poverty program” in which he charged that seven new microscopes the government had bought for schools in his Houston district were in fact “rifle scopes secretly retooled for insurrection.” But if there’s a failure in Branch’s book, it’s that he dwells too briefly upon this theme. For all his great characters, Branch decides not to create even one iconic figure of what would become the great white backlash–the defining feature of politics for the next quarter-century.

Even so, Branch nails most of the big stuff–perhaps most important of all, he understands the way historic certainty gusted through the capital in the mid-1960s, and then shifted direction. Here is Lyndon Johnson, in 1965, trying to convince George Wallace to stop attacking federal efforts to register black voters in Alabama: “‘What do you want left when you die?’ Johnson intoned. ‘Do you want a great big marble monument that reads, ‘George Wallace–He Built,’ or do you want a little piece of scrawny pine board that reads, ‘George Wallace–He Hated?”” Johnson was no natural progressive, but, for a fleeting moment he and most members of Congress felt strongly that history was moving left, and all pols who wanted to keep their seats had better get on board. In Branch’s expert hands, the next three years of American history are the diffusion of that certainty and the political momentum it would bring–and that progressives have spent the last 40 years trying in vain to recapture.