In Means of Ascent, Book Two of The Years of Lyndon Johnson, Robert A. Caro brings alive Lyndon Johnson in his wilderness years.   Here, Johnson's almost mythic personality--part genius, part behemoth, at once hotly emotional and icily calculating--is seen at its most nakedly ambitious. This multifaceted book carries the President-to-be from the aftermath of his devastating defeat in his 1941 campaign for the Senate-the despair it engendered in him, and the grueling test of his spirit that followed as political doors slammed shut-through his service in World War II (and his artful embellishment of his record) to the foundation of his fortune (and the actual facts behind the myth he created about it).   The culminating drama--the explosive heart of the book--is Caro's illumination, based on extraordinarily detailed investigation, of one of the great political mysteries of the century. Having immersed himself in Johnson's life and world, Caro is able to reveal the true story of the fiercely contested 1948 senatorial election, for years shrouded in rumor, which Johnson was not believed capable of winning, which he "had to" win or face certain political death, and which he did win-by 87 votes, the "87 votes that changed history."   Telling that epic story "in riveting and eye-opening detail," Caro returns to the American consciousness a magnificent lost hero. He focuses closely not only on Johnson, whom we see harnessing every last particle of his strategic brilliance and energy, but on Johnson's "unbeatable" opponent, the beloved former Texas Governor Coke Stevenson, who embodied in his own life the myth of the cowboy knight and was himself a legend for his unfaltering integrity. And ultimately, as the political duel between the two men quickens--carrying with it all the confrontational and moral drama of the perfect Western--Caro makes us witness to a momentous turning point in American politics: the tragic last stand of the old politics versus the new--the politics of issue versus the politics of image, mass manipulation, money and electronic dazzle.