No family name has dominated national politics in the 20th century like the Kennedy's, and no decade was defined by them more than the 1960s.

If you'd ask Senator Ted Kennedy in the summer of 1969 what he saw from where he stood he might have reluctantly answered the White House.

But in Chappaquiddick, the new film by director John Curran (it opens Friday, April 6), we watch that bright vision of the future being snatched away by circumstances when tragic events overtake him that change the course of his life and then unmendably alter his political career path.

A young Edward Kennedy.

A young Edward Kennedy.

Director Curran is on record as being an admirer of the both the Kennedy family and his subject, but nevertheless he has crafted a new film that takes a hard look at Kennedy's actions on that fateful night that is so damning and so well crafted it threatens to offer to final word on the tragic subject.

History records the details of what happened on that night in July 18, 1969. Mary Jo Kopechne, 29, was a talented campaign specialist on Robert F. Kennedy's presidential run that Ted had maintained his ties to after his brother's assassination. In the new film we see Kennedy woo her as potential staff pick for a projected presidential run.

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At a private party held on Martha's Vineyard we are led to infer that Kennedy is also wooing Kopechne in a romantic way too, although this is never explicitly stated. At a certain point we see him and Mary Jo take a drive, drink some whiskey and then head toward the bridge where his car quickly careens off the road into the dark water below.

What happens next has baffled most historians for decades and may always. We know that the car hit the water with Kennedy driving and Kopechne in the passenger seat, but in the film we are offered a series of increasingly frantic flashbacks that actually add to the enduring mystery even as they attempt to explain it.

What you see is often determined by where you stand, Chappaquiddick reminds us, and nowhere is this more true than in politics. “Family,” Ted says to his most trusted inner circle operatives earlier on, “There is no more important word.” But the ties that bind can quickly unravel when the big boss finds himself in the line of fire, the film reminds us.

It's important to remember now how much the Kennedy's were – and are - hated in certain circles in this country, and the events of the 1960's left have no one in any doubt about that. This upstart Irish American dynasty was loved and loathed in equal measure and with an intensity that no other political family has ever been able to replicate, even now.

“What's it like walking in that shadow,” an interviewer asks Ted Kennedy (played by Australian born actor Jason Clark, who has an uncanny likeness to his subject) about his brother JFK in the new film. Instead of answering, the surviving Kennedy concludes the interview saying, “I think you have what you need now, Bob.”

The elusiveness isn't just down to irritation. No one was more aware of the weighty legacy he was carrying than the last living brother of the Kennedy clan.

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By the summer of 1969 the Kennedy decade has concluded with a double murder and talk of a possible run for the presidency in 1972. But in Curran's film we see a Kennedy who is floundering under the weight of other people's dreams. He is at best ambivalent, at worst scornful.

When the accident happens, and the film does not suggest it was anything other than an accident, Kennedy eventually abandons the crash scene to go in search of his fixer and cousin Joe Gargan. Instead of explaining to his cousin what happened the film simply has Kennedy make the following statement, “I'm not going to be president.”

Edward Kennedy speaking to the press.

Edward Kennedy speaking to the press.

By the end of the 60's the pitilessness of what has befallen his extended family has the Kennedy under the microscope in Chappaquiddick questioning if indeed there really is a curse on his family. Ethel, his sister, has been widowed with eleven children to raise and moves around like the victim of an explosion, and JFK's widow is the same.

What the film puzzles over, and invites us to do likewise, is the length of time it takes Kennedy to report the death of Mary Jo. Did he purposely kill her to silence some controversy? Did he save himself and fail to save her? Did he panic? Did he suffer from shock or a concussion? Did he struggle valiant;y for as long as he could to no avail?

Director Curran doesn't make it easy for us. In flashback after flashback we see Kopechne, played affectingly by actress Kate Mara, panic and struggle for her life as the upturned car fills with seawater. She says the lords prayer as tries to keep her head about the advancing waterline. Curran makes us feel her terror up close.

It's what follows next that damages Kennedy's standing, a task made all the more bitter because it is performed by an admirer. Curran shows Kennedy telephoning the family patriarch, Joe Sr. “Dad I got myself into the deepest kind of trouble,” he tells his ailing father. “One of the secretaries is dead. I was driving. I had too much to drink I think...”

The line is silent on the other end until Joe Sr. who has been felled by a stroke, gets one word out. “Alibi!” he shouts.

That exchange is possibly the most damning in the film. Following his father's directive we see Ted prevaricate and backtrack for the next forty minutes. Will he lie about who was driving? Yes. Will he lie about exactly where he was and what he was doing? Yes. Will he plot an unconvincing cover up until the truth overtakes him? Yes. Will he fake an injury? Yes. Will he surrender his integrity to save his career? You decide.

Jason Clarke playing Edward Kennedy in "Chappaquiddick".

Jason Clarke playing Edward Kennedy in "Chappaquiddick".

Watching his room full of top advisors, all of them men, plot his course away from the looming iceberg and toward 1600 Pennsylvania Avenue is mostly nauseating. And as irony would have it just as his own fortunes are under scrutiny a signature aim of his brothers legacy is being fulfilled in the Apollo moon landing.

This kind of contrast is what makes Chappaquiddick so shattering. As his closest family member Joe Gargan looks on, we watch a good man lose sight of who he is and what he stands for in the hope, against hope, that he can navigate away from his worst night toward a future where he will still offer his best.

“If you do this right you might be more electable,” says an advisor before Kennedy goes live to the nation, ready to give his version of events in the hope of national reprieve. That comment and other's like it leaven a wide and distinguished senatorial career with the kind of real politick that has come to poison our own cynical times. Chappaquiddick isn't comfortable viewing, but it is essential viewing.

Read more: What you should know about John F Kennedy

Senator Edward KennedyFlickr.com