Chappaquiddick & Mary Jo Kopechne: why Kennedy never became president

Senator Edward Kennedy, who has died after a long battle with a brain tumour, was always expected to follow his elder brothers Jack and Robert - both assassinated in the 1960s - to the highest level of political life. But then came the Chappaquiddick incident, a scandal from which he never was able to recover.

"As long as I am in public life, the incident will be raised," he once admitted, and he couldn't have been more right.

The precise details of what happened on the night of July 18, 1969, have now gone to the grave with the 77-year-old senator. What is known for certain is this:

Kennedy, already a senator at 37, attended a party on Martha's Vineyard, the holiday island off the coast of Massachusetts where Barack Obama and his family are currently spending their summer holiday. The party was held on Chappaquiddick Island, which is linked to the eastern tip of the main island by the narrow Dike Bridge.

The party was being held for the so-called 'Boiler Room Girls', a group of young women who had worked on his brother Robert Kennedy's presidential campaign before he was shot in June the previous year.

Late that night, after leaving the party with 28-year-old Mary Jo Kopechne, Kennedy drove his black Oldsmobile sedan off the Dike Bridge. The car was not found until the next morning, July 19, when it was spotted overturned and submerged in the water beside the bridge, with Kopechne's body inside.

A short while after the discovery, Kennedy walked into the Edgartown police station on Martha's Vineyard and said that he had been the driver of the car.

The scandal erupted because Kennedy, who had a reputation for drinking, did not immediately report the accident. It got worse when it became clear that Kennedy had extricated himself from the submerged car and swum to safety - but was unable to prevent Kopechne drowning.

Rumours abounded that Kennedy and Kopechne were involved in a sexual act when the car went off the bridge. But while the young senator pleaded guilty on July 25 to leaving the scene of an accident, he denied driving under the influence of drink or any 'immoral conduct'.

In a national broadcast following the court hearing, he said: "I regard as indefensible the fact that I did not report the accident to the police immediately."

The following January, an inquest into Kopechne's death was held at Edgartown under Judge James A Boyle. At the request of Kennedy's lawyers, the inquest was conducted in private.

The inquest report was held back until a grand jury had convened on Martha's Vineyard in April the same year. When the grand jury decided against issuing any indictment, Judge Boyle released his report, in which he concluded that some aspects of Kennedy's version of what happened on July 18-19 were not true, and that "negligent driving appears to have contributed to the death of Mary Jo Kopechne".

Kennedy stated that Judge Boyle's conclusions were "not justified".

Locally, where the Kennedy dynasty was revered, the Chappaquiddick incident did not harm him politically: he was easily re-elected to a further Senate term in 1970, and went on to remain the senior senator for Massachusetts until his death. In 2006, Time magazine named him one of America's Ten Best Senators for his "titanic record of legislation". President Obama, who said today he was heartbroken by Kennedy's death, called him "the greatest United States senator of our time".

Nationally, however, public doubts about his behaviour that night never went away. His only attempt to run for the White House was a miserable failure when he lost to the incumbent Jimmy Carter in the 1980 presidential primaries.