Years before Watergate, the name Chappaquiddick became shorthand for political scandal.

Taking its name from the Massachusetts island where Ted Kennedy drove his car off a bridge, resulting in the death of his passenger, Mary Jo Kopechne, the movie “Chappaquiddick” dramatizes the incident and its scandalous fallout.

The Kennedy dynasty has its share of admirers and critics alike, and the movie doesn’t appease either camp. The result is a challenging character study, punctuated by moments of uneasy suspense and dark humor.

The film portrays Kennedy as a complex, contradictory figure. It is the summer of 1969, and Kennedy (Jason Clarke) is still reeling from the assassination of his brother Bobby a year earlier. In his late 30s, Kennedy is already a Massachusetts senator, and his friends believe he is positioned for a presidential run.

After a boat race, Kennedy and his friends have a party on Chappaquiddick. He offers a ride to Kopechne (Kate Mara), one of Bobby’s former secretaries, and off they go. An accident seems inevitable because Kennedy is drunk, and, sure enough, his car veers into a pond. He escapes, but she drowns.

The film follows Kennedy as he tries to pre-empt the backlash, maintaining his sympathetic public persona.

Clarke (“Zero Dark Thirty”) avoids caricature, portraying Kennedy as a man who loathes — yet takes advantage of — the heavy expectations that fall on his shoulders. While he experiences genuine grief over Kopechne’s death, it does not hinder his capacity for slick manipulation.

The screenplay (by Taylor Allen and Andrew Logan, both getting their first credit for a feature-length movie) strongly implies that Kennedy was still in a depressive state in 1969, and that his mind-set was focused more on family than politics. Bruce Dern plays his father, Joe Kennedy — the family patriarch, enfeebled by a stroke — as a hateful man whose impaired speaking ability intensifies his anger. His disappointment in his son helps makes Ted Kennedy more sympathetic: a wayward figure who wants to do good.

But director John Curran (“The Painted Veil”) never lets that sympathy last long. In the moments after the accident, while Kennedy is wandering the island, Curran cuts to footage of Kopechne’s death, and we hear her whispering in her last breaths. The depiction of this moment is harrowing in its pitilessness.

As the press descends on the island and Kennedy admits to leaving the scene of a crash, frustration gives way to exasperation. In one wry scene, Robert McNamara (Clancy Brown) tries to work out how to spin the scandal, with Kennedy not helping. “The Bay of Pigs was handled better than this,” McNamara fumes.

Other Kennedy stalwarts, including confidante Joe Gargan (Ed Helms dialing back his comic persona) and JFK’s former speechwriter Ted Sorensen (Taylor Nichols), make appearances, and it is in their subtle disappointment that the movie finds a certain truth about public life: No one dares say what they are really thinking.

“Chappaquiddick” provides just enough detail to allow us to draw our own conclusions, yet no viewer will think of Kennedy in quite the same way. For a true-crime film about a well documented incident, its ability to preserve ambiguity is remarkable in itself.