NEW YORK As he watched the breach and then the break between Sen. Barack Obama and the Rev. Jeremiah A. Wright, former White House speechwriter Ted Sorensen was reminded, as he is so often, of his years with John F. Kennedy.

It was September 1960. Kennedy was addressing a gathering of ministers in Houston, responding to concerns that a Catholic could be trusted as president -- a major obstacle then for Kennedy's campaign.

"All of those conservative Protestants were glaring at him in the audience," recalls Sorensen, speaking from the living room of his apartment overlooking Central Park, light rain falling on a cool spring morning.

"And he referred to the fact that a lot of these pamphlets quoting popes and priests and prelates from the Catholic church were from other countries, and sometimes other centuries, and then he said, 'I do not consider these other quotations binding upon my public acts. Why should you?' "

"And I've always felt that that's what Obama should say about Reverend Wright," Sorensen says of Obama's former pastor, whom the candidate denounced after Wright suggested that the U.S. government invented the AIDS virus to destroy blacks and made other inflammatory remarks.

Few people were affected more profoundly by the life, and death, of Kennedy than Sorensen, the studious young aide whose liberal ideas and poetic turns of phrase became so entwined with Kennedy's that the president called him his "intellectual blood bank."

Sorensen turns 80 this spring, but over the decades he has changed little in appearance -- fit and slender in a blue polo shirt and tan slacks, grayish hair brushed back -- and in his ideals and adoration for his former boss.

Author of a Kennedy biography that came out in 1965, just two years after the president's assassination, Sorensen has for years kept details about himself and about Kennedy away from the public. He has ended his silence with "Counselor: A Life at the Edge of History" (576 pages, Harper, $27.95), a memoir that in its own way was as difficult to write as the first book.

In the 1960s, he worked through grief and around the sensitivities of widow Jacqueline Kennedy and brother Robert Kennedy, both of whom were still alive. "Counselor" was a great debate with his own body: A stroke in 2001 left him unable to read his own handwriting and forced him to dictate the memoir.

"Everything else I had ever written I had written in longhand, in lined yellow pads, and I edited myself as I went along," he says. "This book took me six years, and I've written several other books, including a very long one [on Kennedy] that took me a year and a half."

Released with an announced first printing of 150,000 copies, "Counselor" begins with Sorensen's childhood in Nebraska and continues to the present, and has blurbs from historian Robert Caro and Obama. Sorensen is a supporter of Obama and campaigned for him in Iowa.

Acknowledging that even Jacqueline Kennedy believed he had a childlike worship of her husband, Sorensen says his "strong feeling for the man and about the man was totally based in fact, and deserved." He declines to discuss Kennedy's private failings during the interview, but he writes about them in his memoir, with sadness and sympathy.

Yes, Kennedy cheated on his wife, and Sorensen suspected it in his lifetime. He knows nothing about the president's legendary liaison with Marilyn Monroe but does confide in his book that "after 1956 I was vaguely aware of a few flings and fancies along the campaign trail" and that "I knew briefly a few of those who I assumed to have shared his bed."

"After all these years, it is unpleasant for me to acknowledge even these limited observations of his philandering," Sorensen writes. "It was wrong, and he knew it was wrong, which is why he went to great lengths to keep it hidden. . . . In every other aspect of his life, he was honest and truthful, especially in his job. His mistakes do not make his accomplishments less admirable; but they were still mistakes."

Despite all the revelations about Kennedy, Sorensen's appreciation has only deepened. He finds no president over the past 40 years who meets his former boss' standards of courage, wit and integrity. Even Robert F. Kennedy, murdered in 1968 during his own presidential run, would not have matched his brother, Sorensen says.

He writes lovingly, and slightly warily, of Jacqueline Kennedy, whom he thinks of with "awe, admiration and affection." She was "strong-willed, but never arrogant, gentle but never weak."

She was also highly protective of her husband's legacy, suggesting numerous deletions in Sorensen's 1965 biography, especially positive references to his successor, Lyndon B. Johnson. In the 1980s, she reacted angrily to Sorensen's plan to publish a collection of Kennedy speeches, accusing of him of exploiting her late husband and only changing her mind after family members intervened.

Readers will learn a lot from his memoir; Sorensen already has. As he looked through the presidential archives, Sorensen discovered, to his great surprise, that Kennedy had considered appointing him national security adviser. He also identified an unpopular man in the Kennedy administration: himself.

"I discovered that a lot of people didn't like me. I was really taken aback and saddened by that," says Sorensen, who writes of being known as "not the warmest human being" among fellow aides.

"But in addition, writing a book about your whole life really gives you a different perspective about certain themes.."