Theodore C. Sorensen, special counsel, advisor, speechwriter and "alter ego" to John F. Kennedy, died today at the age of 82 at a New York hospital from complications of a stroke he suffered last week.
Sorensen, who is survived by his widow, Gillian Sorensen, had also suffered a stroke in 2001 that left him with poor eyesight and hindered his ability to write his autobiography.
A key aide during his 1960 presidential campaign, and special counsel and speechwriter to Kennedy between 1961 and 1963, Sorenson was a close confidant, rivaled only by JFK's brother Robert, throughout the Cold War, the growing civil rights movement and the Cuban missile crisis.
"I was so saddened to learn that Ted Sorensen passed away," President Obama said in a statement released this morning. "I got to know Ted after he endorsed my campaign early on. He was just as I hoped he'd be -- just as quick-witted, just as serious of purpose, just as determined to keep America true to our highest ideals.
"Even as I mourn his loss, I know his legacy will live on in the words he wrote, the causes he advanced, and the hearts of anyone who is inspired by the promise of a new frontier," he added.
Born in Nebraska in 1928 to Christian A. Sorensen, a progressive politician and future attorney general of Nebraska, Ted Sorenson received both his Bachelor's degree and law degree from the University of Nebraska in Lincoln, where he finished at the top of his class.
"I consider it one of the great privileges of this job that I got the chance to know Ted, hear some of his amazing stories, and seek advice from the best speechwriter who ever lived. Truly an extraordinary life," White House chief speech writer Jon Favreau told ABC News today.
By the time he was 27, Sorenson was researching and drafting Kennedy's Pulitzer Prize winning book, "Profiles in Courage."
A controversy ensued over his role in working on the book, with many claiming that he was the sole writer. In his 2008 autobiography, "Counselor," he wrote that it was in fact collaboration.
The closeness and remarkable trust that developed between the two, along with Sorenson's gift for writing, led to a collaboration that would last for the rest of Kennedy's life.
The majority of Kennedy's memorable speeches and declarations were born out of his collaborations with Sorenson, including his promise to put a man on the moon and his inaugural address, when he famously challenged Americans to "Ask not what your country can do for you; ask what you can do for your country."
While Kennedy referred to Sorensen as "my intellectual blood bank," presidential secretary Evelyn Lincoln said that "Ted was really more shadow than ghost, in the sense that he was never really very far from Kennedy."
Initially focused on the administration's domestic agenda, Sorenson was asked by Kennedy to enter the foreign policy realm after the Bay of Pigs invasion. He wrote Kennedy's correspondence with Soviet Union leader Nikita Khrushchev.
Sorenson said he was devastated by Kennedy's assassination in 1963. He initially submitted a letter of resignation to Lyndon Johnson the day after Kennedy was assassinated, but decided that he would stay on through the transitional period, and he wrote Johnson's first address to Congress, as well as the 1964 State of the Union address.
"[It was] the most deeply traumatic experience of my life. ... I had never considered a future without him," he said of losing Kennedy.
"Sometimes," Sorensen he said to an interviewer in 2006, "I still dream about him."
In his 2008 biography, "Counselor," Sorensen calls his 11 years with Kennedy "the cornerstone of my professional life; and the cornerstone of our relationship was mutual trust. JFK brought me into his inner circle, confiding in me secrets that -- had I discussed them with others -- might have done serious harm to his political career, his public image, or perhaps his marriage."
"What's striking about Sorensen was not just his unique partnership with JFK," said ABC News' John Hendren, "but also his staggering humility and loyalty -- a loyalty that has shown him quietly abstaining from joining in the chatter on the most controversial topics related to JFK."
After resigning from the Johnson administration, Sorenson began his legal career at Paul, Weiss, Rifkind, Wharton & Garrison LLP, which saw him through the next four decades.
He also dabbled on the fringes of politics, advising Robert Kennedy in his 1968 presidential campaign and running for the Democratic nomination for the Senate in New York in the early 1970s.
In 2008 he threw his support behind Barack Obama's Presidential bid, often drawing comparisons between Obama's and Kennedy's presidential campaigns.
Sorenson wrote four books throughout his life, including his 2008 autobiography "Counselor," "Decision Making in the White House" in 1963, "Kennedy" in 1965 and "The Kennedy Legacy" in 1969.
In addition to his wife Gillian, Sorenson is survived by his sons Eric, Stephen, and Philip, and his daughter, Juliet. The Associated Press contributed to this report.