What is the author's tone in Robert Kennedy and His Times by Arthur Meier Schlesinger?

Arthur Schlesinger is, first of all, a historian, a man who experienced and documented the presidencies and American political history, from Franklin Roosevelt forward, and their impact on both domestic and international relations. He was, admittedly, a liberal Democrat, and his focus, in teaching at Harvard, in his involvement in campaigns and the Kennedy White House, and in all of his writings, was to promote the philosophy and politics of liberal Democrats. Lack of objectivity and transparent partisanship is evident in this work; however, this bias does not result in an unworthy piece, but, rather, creates a thorough picture of a multi-faceted personality, focusing more on the achievements and lofty missions than on the political and obsessive aspects of Robert Kennedy's character. Other writers and historians have accused Schlesinger of skewing his portrayals of the Kennedy men because of his "love affair" with the family; however, the evident partisanship would more correctly be attributed to the fact that his political views were so closely aligned to liberals of his times, and these included John, Robert and Ted Kennedy. Having written speeches for all three, having served in the campaigns of all three, and having participated in the John Kennedy administration, Schlesinger becomes more than a mere "Kennedy lover." He becomes an individual supremely qualified to chronicle the life of Robert Kennedy.