Writing a history of left-wing movements is a tricky business, not least because of the notorious problems of determining just what ""left"" means. Lader, whose previous books have championed abortion rights, adopts an extremely broad -- hence vague -- definition: ""The Left . . . is a movement that seeks decisive, lasting, social, political, and economic change for large numbers of oppressed and disadvantaged people."" As straight history, Lader's broad view enables him to cover a great deal, from the likes of Manhattan's radical-maw crick Congressman Vito Marcantonio -- for whom Lader once worked -- to Weatherwoman Bernardine Dohrn; but analytically his breadth weakens his interpretation of the material. Lader begins with the 1946 assault on the Communist Party and its repercussions on the non-Communist left, a period noteworthy for the defensive posture adopted by socialists and liberals alike. Lader is good on the background of the CP's decline, as well as on the roots of the civil rights movement in Old Left organizations. A second, aggressive period dates from the civil rights activism of the Fifties and Sixties, which ushered in new forms of political protest. After detailing the origins of such groups as SNCC, the Black Panters, SDS, et al., Lader follows them through the transformations of the Sixties to their degeneration in disconnected violence. A successful left movement must have a local base, he contends, but his model of Marcantonio's Congressional District is archaic. In some instances, moreover, Lader uses voting statistics to determine success or failure (like the 1948 Wallace campaign), then interprets the adherence of many college students to Eugene McCarthy's cause as a weakening of SDS's campus base. He goes on to criticize SDS for adopting a ""new class"" perspective, then praises the creation of ""liberated spaces"" like San Francisco where gays have attained political power, forgetting that San Francisco has beome the archetypal middle-class city. In short, Lader, like the movements he catalogues, has no theoretical framework for analyzing the political structure of America or the groups that constitute it, shifting back and forth from class- to sexual- to issue-oriented approaches. A good historical review, but an eclectic interpretation.