In the summer of 1969, consiglieres of the former John F. Kennedy administration -- Robert McNamara, Arthur Schlesinger and Ted Sorensen, among others -- convened in Hyannis Port, Mass., to write the apology that would save the young Sen. Ted Kennedy from himself.
Only days before, Kennedy had left the scene of a fatal car crash on the small island of Chappaquiddick on Martha's Vineyard, taking the life of 28-year-old Mary Jo Kopechne.
The second-term senator waited nearly 10 hours to report the accident and offered virtually no explanation other than he "panicked."
"In those conclaves a speech, not unlike the 'Checkers' speech, was crafted for him to give on TV, throwing himself on the compassion of the American people to write and call in to keep him on the ticket," said Edward Klein, author of the new book, "Ted Kennedy: The Dream That Never Died."
"All of the Kennedy acolytes were there," Klein told ABCNews.com. "His wife Joan was not allowed downstairs. They didn't want her to hear it."
The details of the July 19 accident were salacious: a Regatta Weekend reunion party at a friend's cottage with all married men (except one) and six women -- the "boiler room girls" -- who had worked together on Robert Kennedy's 1968 presidential campaign.
After a day of sailing and heavy drinking, Kennedy drove his black Oldsmobile sedan off a small wooden bridge into Poucho Pond, trapping Kopechne in seven feet of water.
Edward Moore Kennedy -- only 38 and up for re-election the following year-- had violated one of the cardinal rules in politics: "Never get caught with a dead girl or a live boy."
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"Down through history we have had leaders who were flawed in their personal life and brilliant in public life," said Klein.
"How could he be one of most trusted members of Senate -- and they trusted his word as good as gold -- be an out-of-control frat boy most of his life?" he asked. "Life is complicated and people aren't as simple as we'd like them to be."
After that night, the word Chappaquiddick became synonymous with deception and abuse of power, and for decades until this day, each major anniversary was dredged up in newspapers around the country.
But oddly, the darkest moment in Kennedy's career also sealed his fate as a work-horse senator and ultimately transformed him into one of the most highly regarded politicians in Congress.
"For all of us, either it would make you or break you," said presidential historian Richard Norton Smith, a consultant for ABCNews.com.
"Few of us experience something as soul-testing as that, but when we can weigh it against the succeeding 40 years and draw some linkage, who would believe this story would end this way, so essentially triumphant?"
On July 26, 1969, Kennedy delivered the television speech that saved his senatorial seat. Speaking to the nation for just 13 minutes, he described a cookout "for a devoted group of Kennedy campaign secretaries" and denied the rumors of drunk driving or "immoral conduct."
He acknowledged his failure to report the accident promptly as "indefensible" and described the "irrational" thoughts that consumed him that night, such as wondering "whether some awful curse did actually hang over all the Kennedys."
With the 1970 Senate election looming, he asked the voters what to do next.
In telegrams, letters and telephone calls Massachusetts voters overwhelmingly supported Kennedy's run for Senate, 100-1.
"It saved his bacon," said Klein.
Kennedy easily won by a landslide with 62 percent of the vote, but the scandal dogged him, derailing his presidential bid against Jimmy Carter in 1980, even preventing him from becoming the Democrats' Senate Whip in 1971.
But before July 1969, the youngest son in the Kennedy dynasty was on a clear path to the presidency. The eloquent eulogy for his slain brother Robert, only the year before, had transfixed the nation and, according to polls, 79 percent of all Americans thought he would be the Democratic nominee in 1972.
"There was all this rising, boiling feeling about this meteor getting ready to take off," former Kennedy aide Robert Bates told the Boston Globe recently. "Everybody wanted to be connected with Ted."
In that tragedy drowned the highest aspirations of the last Kennedy son, a reckless personality whose reputation had already been mired by other scandals: expulsion after college cheating and reports of excessive womanizing and drinking.
The political fall-out echoed his first run for Senate in 1962, when his primary opponent, the late Eddie McCormack, sneered, "If his name was Edward Moore instead of Edward Moore Kennedy, he'd be a joke."
Even his own brothers deemed "Teddy" too immature for the Senate seat left vacant by JFK's election in 1960, but were over-ruled by family patriarch Joe Kennedy, according to the new book "The Last Lion" by Boston Globe reporters.
The president-elect asked Massachusetts Gov. Foster Furcolo to appoint family friend Benjamin A. Smith until Kennedy turned 30 in February 1962 and was old enough to run in a special election.
Just days after the televised apology, a Time-Harris poll revealed 51 percent of Americans did not believe Kennedy's explanation of why he was at a party with single girls, how a man so familiar with the island could have taken a wrong turn and how, with a back brace from a 1964 plane crash, Kennedy could have swum the turbulent sea waters to his hotel.
Even those who had faith in the senator worried about his ability to handle a crisis. Friends testified in an inquest that after the accident a confused and crying Kennedy, trying to blame the accident on others begged, "What am I going to do, what can I do?"
Within five days of the accident, Kennedy's lawyers arranged for him to plead guilty to leaving the scene of the accident involving personal injury with a two-month suspended sentence and one-year probation.
No further charges were brought against the senator, even after an inquest that raised numerous questions about Kennedy's account of the events and a grand jury the following year.
His wife Joan, mother of their now three children, suffered a miscarriage after the couple attended Kopechne's funeral, and she blamed it on Chappaquiddick.
Although the Kopechnes said publicly they had only received a small amount of money from Kennedy to use for the down payment on a house, his political opponents charged that the family had paid off the victims' family to keep quiet.
In the coming months, unanswered questions fed conspiracy theories, a slew of books on the topic and indignation in the national press.
A Newsweek cover story claimed Kennedy's friends had recently been "powerfully concerned with his indulgent drinking habits, his daredevil driving, and his ever-ready eye for a pretty face."
To many, those words would later ring true, when in 1991 Kennedy was present at a late-night hotel drinking binge with his nephew William Kennedy Smith, who was charged, but later acquitted of rape.
Press attention rippled across the island to the mainland, where Kopechne, the only daughter of a middle-class New Jersey family, was described by friends as "sweet" and a teetotaler.
Though no autopsy was ever done, her alcohol level was .09 percent, according to records at the time, about the equivalent of three to five drinks. Because of the 10-hour lag in reporting the accident, Kennedy's blood alcohol levels were never tested.
Americans were horrified when they learned that rescue workers found her body in the well of the back seat with her head held up, perhaps indicating that she had been alive for some time breathing in an air pocket.
The world press descended on the small, resort island. Tourists chipped away pieces of wood off Dyke Bridge and even stole bits of shattered glass from Kennedy's black Oldsmobile, which for days lay unprotected.
Gail Lance Huntoon was a 17-year-old working the front desk at her grandmother's hotel -- The Katama Shores on South Beach -- where Mary Jo Kopechne had a reservation to stay that ill-fated night.
"It was ridiculous," she told ABCNews.com. "Everything he said was a lie. People were really appalled because no charges were filed because he was a senator."
But today at 57, Lance Huntoon, whose family still lives on the island, views him differently.
"We were right there and it was so intense, but I really do have a softer opinion of him," she said. "He really tried to pay back in public service."
Many of those involved were unwilling to talk about the details of Chappaquiddick, including Sorensen, now 81, who helped craft the pivotal television address. But he lauded Kennedy's efforts to reinvent himself in its aftermath.
"He is a much more distinguished, decisive, solid leader in this country than he was prior to the 1969 accident," said Sorensen, who served as John F. Kennedy's speech writer and special counsel.
"Lots of people have tragic encounters with fate," he told ABCNews.com. "Some are ruined and never recover from it. Ted knew and accepted the fact that he would never succeed to the ambition of his brother that had first been planted in his mind."
"But it didn't cause him to give up on public life," he said. "He didn't go back to taking it easy as a wealthy, famous man and taking his leisure on the beach. He worked harder than ever because he was a fighter for the causes of his brothers John and Bobby, reaching out to blacks, the poor and unemployed. He became the concerned uncle for the children in his life and showed compassion for people at the bottom of the economic pyramid."
Though the 1980 Democratic presidential nomination eluded him, Kennedy's riveting convention speech became a clarion call for for the liberal wing of the party and the hallmark of his career forward.
"For me, a few hours ago, this campaign came to an end," said Kennedy. "For all those whose cares have been our concern, the work goes on, the cause endures, the hope still lives, and the dream shall never die."
Sorensen credits Kennedy's early endorsement of Democratic candidate Barack Obama as giving political clout to the now president's 2008 victory.
Still, Chappaquiddick caused Kennedy, who had "moved swiftly up the ladder," to have no chance at an official leadership post. He was passed over in 1971 for the Democratic whip position to Sen. Robert Byrd, D-W. Va., and ruled out as a future minority leader, according to Norm Ornstein, a congressional analyst for the American Enterprise Institute.
"It was a set-back, but actually, in some important ways, it helped to make his career as a senator and caused him to rethink other elements of his life and become a workhorse again for policy instead of leadership," he told ABCNews.com.
Chappaquiddick has become "the secondary story of his life," said Ornstein. "There is certainly no question that he had pretty wild elements through some years in his career. He clearly has a stamina level more than anyone else I ever met, and it didn't shrink his ability to do work and shape legislation when partying."
Even his opposition could find little fault with the senator. "It's impossible not to love him," said Ornstein, just before Kennedy's death.
"He's a dynamic, infectiously funny person who just envelops you," he said. "He really's got tremendous personal charm."
At the same time, a new generation of Americans has little or no memory of Chappaquiddick.
"There were so many vicissitudes in his life -- drinking, problems with his first wife, the loss of two brothers," said Jeff Berry, professor of political science at Tufts University. "It was quite a roller coaster of a life."
"Today there are people who survive and come back from their indiscretions," Berry told ABCNews.com. "Time is a gentle father."
"I don't think it damaged him for his whole career," he said. "Gradually, over time, he has grown into the dean of the Democratic Party."
In the past few elections, Kennedy has faced virtually no opposition in his home state and even when Mitt Romney campaigned against him 1994, "nobody had any interest in tarnishing him," said Berry. "Romney knew that would backfire."
The political return of the nation's prodigal son, against the backdrop of today's 24-hour news cycle, opinionated cable television and the blogosphere, may not be that surprising.
"In some ways it was the event on which [his life] pivots," said historian Norton Smith. "We didn't know it at the time, but it effectively precluded him from even becoming president, and yet from the perspective of 40 years, who would ever have imagined on that weekend in 1969 he would go on to be such an important figure, and not only in the U.S. Senate. He is universally regarded as a giant."
"He found himself in the ideological minority," he said. "His brand of liberalism was derided as out of touch and yet somehow he managed over and over again, often working across the aisle, with people who didn't share his convictions," he said. "In the end, it turned out fate had something else in store for him."