Everything they did seemed to be news, even if it was just Jackie sporting a miniskirt in public (autumn 1966 and “cautious housewives over 30” followed suit, The New York Times noted later). This intense level of scrutiny, sparked by President John F. Kennedy’s 1963 assassination and fuelled by a yearning both for what once was and might just be again, kept the Kennedys in the spotlight.

Book review: The Kennedy Wives – lives of the women behind four very public men

Patience was not a virtue in the 1960s. The decade was all about change: wonderful, horrific, bewildering – often all at the same time. Into that world and time strode Robert Kennedy. He was, as shown by Larry Tye’s new biography, Bobby Kennedy: The Making of a Liberal Icon, a man on a mission even if he wasn’t, perhaps, fully aware of where the mission would go.

“Some people see things as they are and say why?” Kennedy would famously say, paraphrasing George Bernard Shaw. “I dream things that never were and say, why not?”

Tye’s well-researched and carefully sourced book details how Kennedy used such thinking to address the major issues of that rapidly evolving decade. He saw change coming and turned to meet it.

“A revolution is coming – a revolution that will be peaceful if we are wise enough, compassionate if we care enough, successful if we are fortunate enough, but a revolution which is coming whether we will it or not,” Kennedy wrote.

While that “revolution” wasn’t as great as the left hoped for and the right feared, America was a profoundly different place at the end of the decade than at the beginning. Tragically, Robert Kennedy would not live to see the country he was working so hard to change.

RFK children speak about assassination in Dallas

Kennedy’s assassination in 1968, minutes after winning the California Democratic primary for president, cruelly cut short a life that, as Tye so carefully lays out, was one in progress. Kennedy began as a man who, as Tye notes, saw things starkly in basic terms, like good and evil, working for Joseph McCarthy, the Wisconsin Republican who fuelled a communist witch hunt; working tirelessly – ruthlessly, his critics famously said – to get his brother into the White House; and doing anything to score an administration win. At the end of his life, Kennedy was increasingly his own man who, matured by grief and more open to life’s complexities, had become an eloquent champion for the poor and the oppressed.

JFK film mystery: Lost original footage of Kennedy assassination sparks US$10m lawsuit

RFK’s record on civil rights, his wrangling with the Russians over Cuba, his crusade against organised crime, how he waged various Kennedy campaigns – all are examined in this book. It’s clear Kennedy’s metamorphosis to “liberal icon” didn’t happen immediately or easily. Along the way, Kennedy amassed a formidable list of people who disliked or hated him, including Frank Sinatra, secretary of state Dean Rusk, FBI director J. Edgar Hoover, writer Gore Vidal, senator Eugene McCarthy, Teamsters president Jimmy Hoffa and President Lyndon B. Johnson. Yet, he was able to win over countless others because he had the courage to change, to evolve and to respond.

Tye, a Massachusetts-based author and journalist, writes in the book’s preface: “No family in American history has been subject to more gossip, hearsay, and embellishment about their private affairs than the Kennedys.

“Prurient interest aside, they opened themselves to it by asking for the public’s trust and votes. JFK’s illicit sex and cover-ups confirmed our distrust. The question is fairly asked about Bobby, too, precisely because he publicly prized conjugal faithfulness and chided those who didn’t practise it.”

Readers looking for titillation or confirmation of rumours long bandied about will likely be disappointed. Tye dispassionately presents the claim, looks for proof, concludes that “no one knows for sure what happened when the doors were closed”, and moves on.

In a sense Tye has to keep going, for Robert Kennedy’s life moved too quickly to allow the biographer to linger long in the bedroom. And short, how short, his life was. Dead at 42 – how could Kennedy have done so much, so fast, so young? One still marvels – and mourns: the great rounded arc of a long life well-lived was not to be his.