The initial annulment, which effectively wiped off the books the original marriage of the 54-year-old Mr Kennedy, was granted more than a decade ago by an archdiocesal court in Boston. But Sheila Rauch, the former wife of Mr Kennedy, has now won a possibly ground-breaking appeal to the Sacred Roman Rota, the Vatican court. Technically, her ex-husband can seek to have the Rota's ruling overturned by the Apostolic Signatura, the highest court of the Catholic Church apart from Pope Benedict XVI himself. But this is considered unlikely.

Vindication, however belated, has delighted Ms Rauch. "I am very pleased," she told Time magazine which first reported the annulment's reversal. "There was a real marriage. It was a marriage that failed, but as grown-ups we need to take responsibility for that. The annulment process was dishonest, and it was important to stand up and say that." Mr Kennedy's setback is but the latest for a family whose triumphs of a generation ago have now been far outweighed by political tragedy and personal calamities. The toothily handsome eldest son of the murdered Bobby Kennedy, Joe was once seen as a new standard-bearer for what, in a pre-Bush and pre-Clinton era, had been America's most successful political dynasty.

But his controversy sparked by the annulment of his marriage almost certainly hastened the end of his public career.

After a relatively amicable civil divorce in 1991, Ms Rauch learnt that her ex-husband had successfully obtained the religious annulment, on the basis that the union, which had lasted 12 years and produced two children, had been based on "false premises" and thus had never really happened at all. This meant that Mr Kennedy could have a Church marriage with his second wife, Beth Kelly, whom he had wed in a civil ceremony in 1991.

Ms Rauch, however, would not go quietly. Outraged at how a dozen years of her life had been airbrushed out of existence by the Church, she published in 1997 a searing memoir entitled Shattered Faith, describing her ordeal. The case became a cause célèbre, and as women's groups came out in support of Ms Rauch, her former husband's approval ratings tumbled.

In the end the man who had been widely touted as a future Massachusetts governor, and more, decided not to seek relection to the House seat he had held since 1987, and in 1999 he returned to private life, and the helm of Citizens' Energy Corporation, a non-profit energy company he had founded in 1979, where Mr Kennedy, now 54, remains to this day.

For all the well-publicised personal travails of the Kennedy family, especially its younger members, the Rota's ruling was something of a surprise, given the powerful connections of the clan to the Catholic establishment, and the fact that Ms Rauch is an Episcopalian.

The affair has also cast a spotlight on the long-standing tensions between the Rome's strict official doctrines on social issues such as marriage and abortion, and the more liberal attitudes of American Catholics - and on the tacit accommodations that have been reached, in the interests of preserving harmony between the Church and its wealthy followers in the US, whose financial support is so important to Vatican operations.

There are eight million divorced and remarried Catholics in the US; although the country contains only 6 per cent of the world's Catholics, it accounts for three-quarters of all annulments sanctioned by the Vatican each year. In 1968, the American Catholic Church granted only 600 annulments a year. That figure is now 60,000.

The issue cropped up in 2004 when it emerged that John Kerry, a Catholic and Democratic presidential candidate, had obtained an annulment of his first marriage. It might arise this time around as well. Another Catholic, the former New York mayor Rudolph Giuliani, is the front-runner for the Republican nomination in 2008. He has had one of his two previous marriages annulled.