All through Lyndon Johnson’s political life,” Robert Caro writes near the end of this magisterial volume covering Lyndon Johnson’s Senate years (1949-1960), “there had been striking evidence not only of compassion but of something that could make compassion meaningful: signs of a most unusual capacity, a very rare gift, for using the powers of government to help the downtrodden and the dispossessed.”

There, in one sentence, is both what is wrong with Johnson and what is wrong with Caro’s otherwise extraordinary biography, a lifetime project that has now reached its third volume. There is nothing at all “rare” about using the power of government—that is, using other people’s money—to ameliorate the sufferings of Americans. It is the epitome of modern liberalism, and is the defining feature of American politics today—so much so that our current president feels it necessary to define himself as a “compassionate conservative,” which is hard to distinguish from a low-budget liberal.

Johnson’s only “rare gift” was his supreme success at finding new ways to institutionalize the spending of other people’s money. Most of that success came during his presidency, which Caro will treat in future installments. Caro’s first two volumes, The Path to Power and Means of Ascent, are highly critical of Johnson, offering juicy details about the many loathsome features of his character and behavior. This volume, too, is frank in its description of LBJ as power-hungry, cruel, bigoted, ruthless, deceitful, vain, grasping, and even “immoral.” He urinated in public, raged at and belittled his staff, used racist epithets with abandon, stole elections, and collected prodigious sums of campaign money in cash (how much of it may have ended up in Johnson’s own pocket Caro does not speculate). And yet the LBJ who emerges from Caro’s pages atones for these sins through his compassion and his skill at making the dysfunctional U.S. Senate work, as Caro supposes the American Founders meant it to work. Despite Johnson’s pettiness, power-seeking, and unvarnished ambition, Caro puts him on a plane nearly equal to Lincoln: “He was to be the President who, above all Presidents save Lincoln, codified compassion, the President who wrote mercy and justice into the statute books by which America was governed.”

To be sure, Johnson’s Senate career presents a spectacle of unparalleled political mastery, worthy of close study. And Caro’s exhaustive researches and fine-grained narrative are a marvel of the biographer’s art. (His book makes you appreciate the smallness of the most recent Senate majority leaders, Tom Daschle and Trent Lott.) Yet Caro’s description of Johnson’s Senate years cannot sustain LBJ on such a high plateau. This may not be an accident or inconsistency, however. Caro’s approach to LBJ, as many critics have observed, is ambiguous, despite the comparisons to Lincoln (which Caro makes more than once).

Some reviewers (Ronald Steel in The Atlantic, for example) argue that Caro has difficulty understanding or accepting political power. There is much to this criticism. His majestic tale of Johnson could be a cautionary tale of the hazards of power—the hazards to one’s own soul, and to a nation when too much power is accumulated in the government. The deeper source of Caro’s ambiguity is the intellectual problem LBJ poses for liberals. As civil rights leader Roy Wilkins succinctly put it: “With Johnson, you never quite knew if he was out to lift your heart or your wallet.” Caro’s praise and partial admiration for LBJ owes to Caro’s filtering Johnson through a sympathetic liberal lens, portraying LBJ as an agent in the progressive march toward greater “social justice,” a phrase that Caro uses frequently in the expository sections of his narrative.

His attempt to redeem Johnson appears to be part of a quiet trend. Reflecting on the ineptitude of the Carter presidency and the fecklessness of the Clinton presidency has led many liberals to begin reappraising Johnson in a more favorable light. His Great Society delivered more landmark social legislation than even FDR’s New Deal. The disaster of Vietnam and the unrest in the streets in the 1960s, which together fractured the Democratic Party, eclipsed this record for a long time. Yet the judgment John Kenneth Galbraith offered in 1967 is reasserting itself: “Our gains under the Johnson administration on civil rights outweigh our losses on behalf of Marshall Ky.”

That liberals, who distrusted Johnson in the Senate and then hated him in the White House, might come to regard Johnson as their most worthy modern champion is a startling irony. It also presents a huge intellectual problem. Unless it is assumed that “character doesn’t matter,” a way must be found to lessen Johnson’s ugliness. Caro finds it in Johnson’s maneuvering in 1957 to break the hitherto invincible Southern filibuster against civil rights legislation.

Johnson arrived in the Senate in 1949 as a full-throated adherent to the Southern cause. He attacked desegregation and civil rights in his 1948 campaign (in statements he suppressed in the 1960s), and his maiden speech in the Senate was titled “We of the South.” He immediately fell in with Georgia Senator Richard Russell, the captain of the Southern opposition to all civil rights legislation, and, Caro believes, attended meetings of the Southern Caucus, the regular gathering where Southern Senators would plot strategy. (Johnson also denied this in later years.)

Johnson immediately distinguished himself in the Senate as someone who understood how to accumulate power around him and get things done. Some of these “accomplishments” were dubious at best, such as his Red-baiting attack on Federal Power Commission chairman Leland Olds, providing the model for Joseph McCarthy several years later. Caro records LBJ telling Olds after having engineered the destruction of his career: “Lee, I hope you understand there’s nothing personal in this. We’re still friends, aren’t we? It’s only politics, you know.”

More significant in Caro’s narrative is Johnson’s decision to pursue the party leadership post in the Senate, hitherto the graveyard of Senate reputations and careers. Caro’s account of Johnson’s years as majority leader is superb. No one could read a man—understand his motives, his weaknesses (and therefore how to get his vote)—like Johnson. “If you liked politics,” Hubert Humphrey remarked, “it was like sitting at the feet of a giant.” Caro’s summary judgment is that “Johnson transformed the Senate, pulled a nineteenth-century—indeed, in many respects an eighteenth-century—body into the twentieth century.”

Johnson’s decision to break with the South and midwife the 1957 Civil Rights Act is portrayed throughout the book as a naked political calculation on Johnson’s part. Even with Johnson’s already legendary skills at manipulating the Senate, it still seemed like an impossible task. Yet there were many reasons why the political interests fell into line. If LBJ was ever going to have a chance of becoming President, he had to be acceptable to Northern liberals in the Democratic Party—You got to clean him up on civil rights,” in the words of liberal lawyer Joseph Rauh. Southerners were willing to go along because they recognized that Johnson was the only Southerner with a realistic chance to reach the White House, where, Richard Russell assumed, LBJ would protect the interests of the South. Johnson found the lowest common denominator—a weak voting rights bill that Caro himself admits had little effect on black voting registration in Southern states. From this nakedly cynical and self-serving stratagem Caro makes Johnson into “the greatest champion that the liberal senators . . . had had since, almost a century before, there had been a President named Lincoln.”

Caro’s evaluation of LBJ depends on a historical premise, that because of the filibuster rules the Senate prior to Johnson had ceased to operate as the Founders intended. In fact, Caro writes a synoptic history of the Senate that precedes the main narrative about Johnson, arguing that the Senate had become “a mighty dam standing athwart, and stemming, the tides of social justice. [The Senate] empowered, with an immense power, the forces of conservatism and reaction in America.” Caro’s “underbook” about the Senate concludes that the long-running Southern filibuster against civil rights was not a geographic anomaly but the essence of the Senate at work.

With this premise, Caro reveals himself to be a relic of Progressivism. LBJ comes to sight in Caro’s narrative as a supremely talented man bobbing like a cork on the tides of history. This is the basis for both LBJ’s greatness and his shortcomings, as is evident in Caro’s ambivalent comments such as “there were times when [LBJ’s] interests coincided with America’s interests.” The repeated comparison to Lincoln is instructive. In Caro’s hands LBJ was plainly not imbued with great purpose like Lincoln or even like Franklin or Theodore Roosevelt, nor does he have the even-tempered virtues of Eisenhower or Gerald Ford. Instead, LBJ’s success derived from the happy confluence of the tides of history and personal ambition. Abraham Lincoln came to his views about slavery and equality because of a principled understanding of the Constitution and Declaration of Independence. Johnson, by contrast, said that “It’s not the job of a politician to go around saying principled things.” The Constitution, Johnson remarked, is a series of compromises, and this statement suggests that Johnson had little awareness of or regard for the principles behind those compromises.

Caro’s historicist premise makes it impossible to draw meaningful distinctions between Lincoln and LBJ—and will make it impossible, further along in Caro’s epic account, for him to distinguish between civil rights law informed by the principles of natural right and civil rights distorted by the ideology of egalitarianism. While Master of the Senate clearly foreshadows LBJ’s troubled presidency, it also fills readers with skepticism about how Caro will judge the defects of Johnson’s Great Society.

Master of the Senate ends with a vignette that captures the problem with Johnson in a way that Caro probably doesn’t fully appreciate. After the election of 1960, which elevated Johnson to the vice presidency, Johnson went to the Senate Democratic Caucus before resigning his seat and attempted to get the consent of his fellow Senators to continue presiding over the caucus and, in effect, still run the Senate. He was startled when his fellow Senators rebuffed this brazen invitation to violate the separation of powers. It is hard to decide whether LBJ’s greater failing here was lack of respect for constitutional principle, or his complete misreading of his former colleagues. For someone renowned for his ability to read other men, this failure of perception is stunning.

Caro dwells on this episode only as a marker of how fast Johnson lost his political clout on the way to an unhappy vice presidency. But it anticipates the problem that should be at the center of Caro’s forthcoming volumes on Johnson’s presidency: how could such an astute politician persist for so many years in misjudging the nature of his most determined political enemy, North Vietnam’s Ho Chi Minh? Johnson’s White House aide John P. Roche wrote years after LBJ died that he could not make Johnson understand that Ho Chi Minh was a dedicated Leninist. Johnson, Roche recalls, kept asking, “‘What does Ho want?’ as if Ho were a mayor of Chicago holding out for five new post offices.” Such a question could only come from a man for whom politics is merely a nihilistic series of deals, utterly without any principled ground. Although the Vietnam mess is behind us, much of the Johnson legacy in domestic policy, especially the unprincipled civil rights legacy of affirmative action, is still with us. Caro’s thorough narrative will be well worth waiting for, but Master of the Senate leaves us with the feeling that he will resolve neither his ambivalence nor our doubts about this giant figure.