Dallek (History/UCLA; Lone Star Rising, 1991; Ronald Reagan: The Politics of Symbolism, 1984; etc.) thoughtfully finds some common denominators of effective presidential performance. Why have some presidents become perennial heroes and others bywords for failure? Dallek delineates five qualities uniquely important to presidential leadership: vision, pragmatism, consensus, charisma (or the appeal of personality), and trust. Dallek then shows how the greatest presidents, like Washington, Lincoln, and Franklin Roosevelt, have displayed these traits in responding to national challenges as diverse as establishing the infant United States, waging the Civil War, and ending the Great Depression. Dallek also shows presidents failing by displaying an absence of these virtues: Herbert Hoover, for instance, lacked pragmatic flexibility, and John Quincy Adams failed to achieve consensus for his aim of advancing the prosperity of American society. To some extent, Dallek recognizes, the traits of success are contradictory and temper one another (a visionary whose vision leads him too far ahead of the popular consensus will fail, for instance); effective presidential leadership, he suggests, consists of maintaining a delicate balance. Assessing success or failure is also a matter of balance: The greatest presidents have suffered policy failures, sometimes major ones. Also, Dallek acknowledges that the qualities of presidential greatness are ultimately more elusive than his checklist of virtues would imply: Assessments of presidents while in office, have been notoriously inaccurate (Dallek cites disparaging evaluations by contemporaries of Washington, Lincoln, and FDR). Recognizing the ever-changing nature and complexity of the president's task, Dallek concludes that ""the study of how past presidents made large gains and suffered major defeats gives us little more than a useful general guide to executive actions."" A provocative analysis of success and failure in the nation's most difficult job.