LYNDON JOHNSON is an elusive subject for a biographer.Arguably the most talented politician of his generation, he was a bundle of paradoxes. Close associates were often baffled by mood swings; legislative colleagues were startled by nose-to-nose encounters that could flash into invective or ease into cajolery. Even enemies credit Johnson with intense energy and drive, a meticulous grasp of politically relevant detail, a gift for wresting compromise out of confrontation. As Senate majority leader, he built a formidable legislative record, breaking new ground on civil rights, extending federal commitment to New Deal policies, and nurturing commitments to new industrial sectors, such as space exploration. Yet this "master consensus-builder" would end his presidency isolated, embittered, and tragically out of touch. The difficulties in sorting through such a complex character are compounded by the vast documentary record Johnson left. One way to make sense of such complexity is to organize the narrative around a hypothesis and run it through the documents like a magnet through iron filings. Robert Caro's first two volumes of a projected three-volume biography, "The Path to Power" and "Means of Ascent," take this tack. Caro's Johnson is driven: grabbing and peering, embracing, manipulating, wheeling and dealing, with a hunger for power "so fierce and consuming that no consideration of morality or ethics, no cost to himself - or to anyone else - could stand before it." "Lone Star Rising" is - very consciously - not Caro. It is written as if Robert Dallek sifted through the piles of documents Caro left behind and teased out competing views. In 700 pages of text and footnotes, there is barely an unqualified assertion. Occasional paragraphs groan under the weight of one, two, even three "buts," "howevers,yets," and "on the other hands." To readers worn down by Caro's unrelenting negative view of Johnson, these qualifiers seem reassuring symbols of accuracy and balance. "Johnson viewed politics as a dirty business in which only the most manipulative succeeded. He did not come to this simply out of some flaw in his character. He learned it from the rough and tumble that characterized Texas politics in the first half of the twentieth-century, and from his early political mentors in Texas and Washington...." Much of that rough-and-tumble world turned on money. The $5 bills that swung congressional elections in 1932 and 1937 sprung from oil and natural gas concessions, and later from the millions committed to dam and shipbuilding projects - ventures that were transforming Texas from a rural backwater to the cutting edge of new defense and aerospace industries. JOHNSON brokered much of that transition, and a close look at how he reasoned through critical choices for public or private interest should be a core concern of any biography of these pre-presidential years. The evidence Dallek adds to the published record often enhances Caro's account of high corruption: the dubious campaign practices, the thwarted Internal Revenue Service investigation of key Johnson backers Brown and Root Inc., Federal Communications Commission favoritism for Lady Bird's KTBC radio and television interests in Austin, Texas. But this evidence is often so buried in other observations - family ties, ties to political patrons, quirks of personal disposition - that it is not clear what motivations Dallek finds most compelling in accounting for Johnson's public priorities. Johnson's moves on civil rights provide another litmus test of political values, especially for a Southerner with presidential aspirations. As a congressional aid, Johnson used New Deal agricultural and housing laws to help black Texans, and as speaker of the House, he masterminded the trade-offs that broke a Southern filibuster over the 1957 civil-rights bill. Johnson, Dallek writes, was convinced that "the South could never come into the mainstream of American economic and political life until it freed itself from the burden of racial segregation."But he also consistently favored the poll tax and voted against bills that would have boosted black enfranchisement. Dallek rarely breaks out of chronological narrative to ask why civil-rights concerns weighed heavily in one case but not in another. If Caro's solution to the Johnson riddle is to hammer home one explanation, Dallek's is to posit as many as possible. In the end, too much explanation may be no explanation. Dallek's Johnson is nonetheless the most fully - and fairly - realized Johnson to date.