Pulitzer Prize-winning US historian Arthur M Schlesinger Jr has died at the age of 89.
The advisor to former US president John F Kennedy helped define mainstream liberalism during the Cold War and remained an eminent public thinker into the 21st century.
Arthur M Schlesinger
He suffered a heart attack while dining out with family members Wednesday night in Manhattan and died in hospital.
Schlesinger was widely respected as learned and readable, with a panoramic vision of American culture and politics.
He received a National Book Award for Robert Kennedy and His Timesand both a National Book Award and a Pulitzer for A Thousand Days, his memoir/chronicle of President Kennedy's administration. He also won a Pulitzer, in 1946, for The Age of Jackson, his landmark chronicle of Andrew Jackson's administration.
Liberalism declined in his lifetime to the point where politicians feared using the word, but Mr Schlesinger's opinions remained liberal, and influential, whether old ones on the "imperial presidency," or newer ones on the Iraq war.
He criticised President Bush for his doctrine of "preventive war," saying "I think the whole notion of America as the world's judge, jury and executioner is a tragically mistaken notion."
For both historians and Democratic officials, he was a kind of professor emeritus, valued for his professional knowledge and for his personal past.
Being a liberal, Mr Schlesinger once observed, means regarding man as "neither brute nor angel." Whether discussing the Kennedys, Vietnam or the power of the presidency, Mr Schlesinger sought moderation, the middle course.
He blamed the Vietnam War on the moral extremism of the right and left and worried that the executive branch had become "imperial," calling for a "strong presidency within the Constitution." He saw American history itself as a continuing "cycle" between liberal and conservative power.