Ted (Sorensen), a Unitarian from Lincoln, Nebraska, is the son of a former Republican attorney general of that state, but an heir to the progressive tradition of Senator George W. Norris (and organizer of the Lincoln chapter of Americans for Democratic Action). Sorensen was first in his class at the University of Nebraska Law School and came to Washington to work for the Federal Security Agency. He left there in 1953 to join JFK's staff after his election to the Senate. They hit it off magnificently. Sorensen not only had strong social convictions echoing those of the young senator, but a genius for translating them into eloquent and persuasive language. During the Kennedy for President campaign, Ted was in charge of the special task force that developed policy positions and speech drafts for JFK. I must add that nothing eats up material faster than a presidential campaign in which a candidate speaks three or four times a day on subjects ranging from nuclear armaments to conservation. The voters expect not only that he be knowledgeable but that he have new and positive alternatives to present policy. Ted somehow was able to keep up with the demand and to maintain a high level of creativity.

Like O'Donnell, Sorensen wore more than one hat at the White House. He was the coordinator of planning for domestic policy and had a key role in formulating JFK's recommendations to Congress. But he also continued to serve as the principal speech writer. Actually, speeches were not written for the President but with him. He knew what he wanted to say and how he wanted to say it. The role of the speech writer was to organize JFK's thoughts into a rough draft, on which he himself would put the final touches. His revisions would often change it dramatically.

Ted, who did all his writing in longhand on yellow legal pads, had been grinding out words for JFK for eight years and knew his style best. As one reporter wrote, "Sorensen had the glory of words." But he was also widely read and could always find exactly the right classical reference to bring a major point into critical focus.

The worst disaster of that disaster-filled period, the incident that showed John Kennedy that his luck and his judgment had human limitations, and the experience that taught him invaluable lessons for the future, occurred on April 17 in the Zapata Swamp at the Cuban Bay of Pigs. A landing force of some fourteen hundred anti-Castro Cuban exiles, organized, trained, armed, transported and directed by the United States Central Intelligence Agency (CIA), was crushed in less than three days by the vastly more numerous forces of Cuban dictator Fidel Castro. America's powerful military might was useless, but America's involvement was impossible to deny. Both publicly and privately the President asserted sole responsibility. Many wondered, nevertheless, how he could have approved such a plan. Indeed, the hardest question in his own mind after it was all over, he told one reporter, was "How could everybody involved have thought such a plan would succeed?"

What was really important in the Bay of Pigs affair was the very "gap between decision and execution, between planning and reality", which he had deplored in his first State of the Union. John Kennedy was capable of choosing a wrong course but never a stupid one; and to understand how he came to make this decision requires a review not merely of the facts but of the facts and assumptions that were presented to him.

The Eisenhower administration authorized early in 1960 the training and arming of a Cuban exile army of liberation under the direction of the CIA. Shortly before the Presidential election of 1960, it was decided (although Eisenhower was apparently not informed of the decision) that this should be a conventional war force, not a guerrilla band, and its numbers were sharply increased.

On January 20, 1960, John Kennedy inherited the plan, the planners and, most troubling of all, the Cuban exile brigade-an armed force, flying another flag, highly trained in secret Guatemalan bases, eager for one mission only. Unlike an inherited policy statement or Executive Order, this inheritance could not be simply disposed of by Presidential rescission or withdrawal. When briefed on the operation by the CIA as President-elect in Palm Beach, he had been astonished at its magnitude and daring. He told me later that he had grave doubts from that moment on.

But the CIA authors of the landing plan not only presented it to the new President but, as was perhaps natural, advocated it. He was in effect asked whether he was as willing as the Republicans to permit and assist these exiles to free their own island from dictatorship, or whether he was willing to liquidate well-laid preparations, leave Cuba free to subvert the hemisphere, disband an impatient army in training for nearly a year under miserable conditions, and have them spread the word that Kennedy had betrayed their attempt to depose Castro.

John Fitzgerald Kennedy had no fear or premonition of dying. Having narrowly survived death in the war and in the hospital, having tragically suffered the death of a brother and a sister, having been told as a young man that his adrenal deficiency might well cut short his years, he did not need to be reminded that the life he loved was a precious, impermanent gift, not to be wasted for a moment. But neither could he ever again be worried or frightened by the presence of death amidst life. "I know nothing can happen to him," his father once said. "I've stood by his deathbed four times. Each time I said good-bye to him, and he always came back."

John Kennedy could speak of death like all other subjects, candidly, objectively and at times humorously. The possibility of his own assassination he regarded as simply one more way in which his plans for the future might be thwarted. Yet he rarely mentioned death in a personal way and, to my knowledge, never spoke seriously about his own, once he recovered his health. He looked forward to a long life, never talking, for example, about arrangements for his burial or a memorial...

He mentioned more than once - but almost in passing - that no absolute protection was possible, that a determined assassin could always find a way, and that a sniper from a high window or rooftop seemed to him the least preventable. Occasionally he would read one of the dozens of written threats on his life that he received almost every week in the White House. But he regarded assassination as the Secret Service's worry, not his. "Jim Rowley," he quipped, "is most efficient. He has never lost a President." He paid little attention to warnings from racist and rightist groups that his safety could not be guaranteed in their areas.

He went to Caracas where Nixon had been endangered by rioters, he stood overlooking the Berlin Wall within Communist gunshot, he traveled more than 200,000 miles in a dozen foreign countries where anti-American fanatics or publicity-seeking terrorists could always be found, he waded into uncontrolled crowds of handshakers at home and abroad, he advocated policies he knew would provoke venom and violence from their opponents, and he traveled in an open car in Dallas, Texas, where the Lyndon Johnson and Adlai Stevenson had been manhandled by extremists not to prove his courage or to show defiance but because it was his job. "A man does what he must," he had written in Profiles in Courage, "in spite of personal consequences, in spite of... dangers - and that is the basis of all human morality." Life for him had always been dangerous and uncertain, but he was too interested in its opportunities and obligations to be intimidated by its risks.

His trip to Texas, like his mission in life, was a journey of reconciliation - to harmonize the warring factions of Texas Democrats, to dispel the myths of the right wing in one of its strongest citadels, and to broaden the base for his own re-election in 1964.

He (Kennedy) would not have condemned the Dallas police, the FBI and the Secret Service. Certainly there were limitations on their ability to guard an active, strong-willed President in a free society, and certainly to this President his agents were deeply devoted. Yet we can never be certain what prevented a more alert coordination of all the known facts on the Kennedy route and the potential Kennedy assassin.

He would not, finally, have doubted the conclusions of guilt pronounced by the Warren Commission. Certainly the members and staff of that Commission deserve the highest praise for their painstaking investigation and report. Yet, in the Commission's own words, "because of the difficulty of proving negatives to a certainty, the possibility of others being involved ... cannot be established categorically"; and thus we can never be absolutely certain whether some other hand might not have coached, coaxed or coerced the hand of President Kennedy's killer.

Personally I accept the conclusion that no plot or political motive was involved, despite the fact that this makes the deed all the more difficult to accept. For a man as controversial yet beloved as John Kennedy to be killed for no real reason or cause denies us even the slight satisfaction of drawing some meaning or moral from his death. We can say only that he died as he would have wanted to die-at the center of action, being applauded by his friends and assaulted by his foes, carrying his message of reason and progress to the enemy and fulfilling his duty as party leader.

He regarded Dallas' reputation for extremism as a good reason to include it on his schedule, not a good reason to avoid it. For, with all his deep commitments, Kennedy was fanatical on only one subject: his opposition to fanatics, foreign as well as domestic, Negro as well as white, on the Left as well as the Right. He was against violence in foreign relations and in human relations. He asked his countrymen to live peacefully with each other and with the world. Mental illness and crime, racial and religious hatred, economic discontent and class warfare, ignorance and fear of this world's complex burdens, malice and madness in the individual and society-these are the causes contributing to the atmosphere of violence in which a President may be assassinated-and these are the very evils which John Kennedy strove most often to root out.

Theodore Sorensen, universally known as Ted, was one of those men whose brilliant career and great talents were partially clouded by anonymity. Even before his boss, John Fitzgerald Kennedy, became president of the US, Sorensen, who has died aged 82, had to handle tricky questions about how much credit he deserved for a book for which Kennedy won a Pulitzer prize. His share in his master's success was even more acutely raised by the question of his precise role in writing Kennedy's resonant inaugural address of January 1961.

The speech is now acclaimed as one of the classics of American political rhetoric, fit to stand with the outpourings of Daniel Webster, Abraham Lincoln and Franklin Roosevelt. Almost every schoolchild of the 1960s was brought up on that speech, with its key invocation, "Ask not what your country can do for you – ask what you can do for your country. My fellow citizens of the world: ask not what America will do for you, but what together we can do for the freedom of man."

It was characteristic of Sorensen's modesty, and of his wit, and no doubt of his boredom with the subject, that when – many years after Kennedy's assassination in November 1963 – an interviewer asked him what his part had been in the writing of that speech, he replied: "Ask not!"

It is agreed that several gifted hands, including that of Adlai Stevenson, contributed to it, and that Kennedy dictated it to his secretary, Evelyn Lincoln, on a plane, using a draft written for him by Sorensen. The dispute centres on how much Kennedy used that draft.

In 2005, two rival scholars, after poring over the speech and its antecedents line by line and almost word by word, came to two opposite conclusions. Thurston Clarke proclaimed that new evidence showed that Kennedy was indeed the author. Richard J Tofel, on the other hand, an executive at the Wall Street Journal, found that Kennedy was responsible for no more than 14 of the speech's 51 sentences, and that "if we must identify" one man as the author of the speech, "that man must surely be not John Kennedy but Theodore Sorensen". It seems, though, that the famous "ask not" trope itself had its origin in Kennedy's years at the Choate school, a boarding establishment in Connecticut, whose headteacher liked to urge his pupils to ask "not what Choate does for you, but what you can do for Choate".