“CHAPPAQUIDDICK”

** 1/2

(PG-13, 1:41 minutes)

Ambiguous and damning at once, John Curran’s “Chappaquiddick” plunges us back into the summer of 1969: the season of Woodstock, the moon landing, the Manson murders and the lowest ebb of the Kennedy mythology.

It was six years since the assassination of John F. Kennedy and a year since Bobby was gunned down. But the Kennedy machine churned on. Jack Kennedy’s ambition to reach the moon was being realized by Neil Armstrong. Edward M. (“Teddy”) Kennedy, already seven years a senator having filled his brother’s Massachusetts seat, was Joseph Kennedy’s only living son left and a likely future president.

Those aspirations — and some of the Kennedy dynasty’s noble veneer — effectively crashed when 37-year-old Teddy drove an Oldsmobile off a narrow bridge on a remote beach road on Chappaquiddick Island, off Martha’s Vineyard, late at night on July 18. With him was 28-year-old Mary Jo Kopechne, a former campaign worker for Bobby (played by Kate Mara in the film), who died underwater. Kennedy escaped from the car, submerged in eight feet of water. Whatever his efforts were to free Kopechne, they were futile. It took him 10 hours to report the incident to the police. Kennedy attributed the delay to a concussion and exhaustion.

Chappaquiddick has long loomed in the political imagination as a kind of definitive yet murky scandal. Curran’s film — a profile in cowardice, you might call it — is principally an effort to visualize and understand that evening. It’s a low-key, generally absorbing if somewhat lackluster procedural that ominously reflects on the darker shadows that loom behind even the brightest shining political hopes.

Jason Clarke, the Australian actor of “Zero Dark Thirty” and “Dawn of the Planet of the Apes,” plays Kennedy. We’ve been so awash in hackneyed Kennedy brogues and caricatured portrayals that Clarke’s performance — stout, nuanced, understated almost to a fault — is an unexpected relief. His Teddy is a little more taciturn than the statesman was, but Clarke carries himself with the assumed importance and natural magnetism of a Kennedy.

There are Shakespearean shades to the tale. As seen in the opening television interview, Kennedy is aware that he pales in comparison to his late brothers. After the accident, he lies on the bridge looking up at the moon his brother’s astronauts were at that moment approaching. He’s hard drinking. His wife and children are nowhere near him. His 80-year-old father (Bruce Dern) has the ability to utter few words, as a stroke victim, but he makes each one hurt. “You will never be great,” he tells Teddy after the accident. When his son first calls to tell him about the crash, Joe wheezes only “alibi” and hangs up.

These are elements that make Teddy a sympathetic figure. But “Chappaquiddick,” penned straightforwardly by Taylor Allen and Andrew Logan, casts an equally critical eye on him as he launches into full damage control mode. Teddy’s own initially wrong-footed efforts at controlling the media storm are quickly corrected by some of the Kennedy family operatives who rush in, including Theodore Sorensen (Taylor Nichols) and Robert McNamara (an excellent Clancy Brown). The smoke-filled room takes command, and Teddy takes his marching orders.

Ed Helms plays Kennedy’s cousin and fixer Joe Gargan, who functions like Teddy’s conscience, pleading for accountability and truth. But he’s batted aside with little trouble. A week after the incident, Kennedy pleaded guilty to leaving the scene of an accident and received a two-month suspended sentence. He addressed the nation in a prime-time broadcast and a year later easily won re-election. But partly if not entirely because of Chappaquiddick, he would never be president. Kennedy may well have been the front-runner for denying Nixon a second term. His 1980 presidential campaign fizzled.

But Kennedy, of course, went on to serve four more decades in the Senate. He was one of the longest serving, most influential legislators in 20th-century America. So what’s the legacy of Chappaquiddick? How are Kennedy’s accomplishments to be reconciled with that night? Those aren’t questions much pursued in the largely self-contained “Chappaquiddick.” Curran, the precise and restrained filmmaker of “The Painted Veil” and “Tracks,” is content to let the record speak for itself and perhaps suggest: Some politicians get away with more than they ought to.