The U.S. Senate is so sharply polarized along partisan and ideological lines today that it’s easy to believe it was always this way. But in the turbulent 1960s, even as battles over civil rights and the war in Vietnam dominated American politics, bipartisanship often prevailed. One key reason: two remarkable leaders who remain giants of the Senate—Republican leader Everett Dirksen of Illinois and Democratic leader Mike Mansfield of Montana, the longest-serving majority leader in Senate history, so revered for his integrity, fairness, and modesty that the late Washington Post reporter David Broder called him “the greatest American I ever met.” The political and personal relationship of these party leaders, extraordinary by today’s standards, is the lens through which Marc C. Johnson examines the Senate in that tumultuous time.

Working together, with the Democrat often ceding public leadership to his Republican counterpart, Mansfield and Dirksen passed landmark civil rights and voting rights legislation, created Medicare, and helped bring about a foundational nuclear arms limitation treaty. The two leaders could not have been more different in personality and style: Mansfield, a laconic, soft-spoken, almost shy college history professor, and Dirksen, an aspiring actor known for his flamboyance and sense of humor, dubbed the “Wizard of Ooze” by reporters. Drawing on extensive Senate archives, Johnson explores the congressional careers of these iconic leaders, their intimate relationships with Presidents John F. Kennedy and Lyndon B. Johnson, and their own close professional friendship based on respect, candor, and mutual affection.

A study of politics but also an analysis of different approaches to leadership, this is a portrait of a U.S. Senate that no longer exists—one in which two leaders, while exercising partisan political responsibilities, could still come together to pass groundbreaking legislation—and a reminder of what is possible.