It’s hard to think of a public figure with an image further removed from rock’n’roll than the former US president Jimmy Carter. “With his cardigan sweaters and devout Christian faith, he doesn’t come off as a particularly cool or hip guy,” said Mary Wharton, director of a new film titled Jimmy Carter: Rock & Roll President, to the Guardian. “He wasn’t even a part of the rock generation. But he was curious about it.”

Enough, in fact, to inspire him to take a deep dive into his son Chip’s Bob Dylan albums, absorbing both the honesty of the sound and the meanings behind the songs. It helped that Carter already had a significant knowledge of every genre that influenced stars of the rock generation, including blues, R&B, folk and most profoundly, gospel. His belief in both the beauty and the sociological impact of all those styles helped Carter forge an improbable bond with the biggest rock stars of the 70s, a connection that became central to his ascent to power.

The core of Wharton’s film argues that stars like the Allman Brothers, Bob Dylan and Crosby, Stills & Nash, as well as outlaw country artists like Willie Nelson and Johnny Cash, played a crucial role in getting Carter into the White House in 1976. The Allmans took the lead, performing concerts to raise money for his run for the Democratic nomination when he had scant funds and no national name recognition. “I was practically a non-entity,” Carter says in the film. “But everyone knew the Allman Brothers. When they endorsed me, all the young people said, ‘Well, if the Allman Brothers like him, we can vote for him.”

Even so, the power of the youth vote was just being tested at that point. The previous presidential election, in 1972, in which Republican incumbent Richard Nixon squared off against Democrat George McGovern, was the first national election that saw the voting age drop from 21 to 18. Yet, Nixon won in a landslide. Four years later, in a country weary from Watergate and Nixon’s successor Gerald Ford, there was a far clearer mandate for change. “The youth vote that time was massive,” said Chris Farrell, the movie’s producer. “Eighteen- and 19-year-olds voted for Carter. Then it spread way beyond that.”

Though Carter wasn’t especially young at the time, at 52, his team were, led by head press secretary Jody Powell, who was 23, and chief of staff, Hamilton Jordan, then 32. After Carter won the White House, Rolling Stone put the two staff members on their cover, calling them “The White House Whiz Kids”. “They were young people, speaking to young people,” said Farrell.

Still, the level of support the rock stars gave Carter represented something new. In the late 1960s, when rock became the cutting-edge force in pop culture, its stars were more likely to support a vague notion of revolution, while lobbing the occasional epithet at Nixon. “For them to associate with a politician wasn’t seen as cool,” said Wharton.

But by the mid-70s, rock had become more mainstream, and magazines like Rolling Stone were eager to flex their growing power by backing candidates more aggressively. While many politicians were eager to court the icons of the rock generation, Carter had a distinct advantage. “The fact that he was an independent thinker appealed to these musicians,” Farrell said. “He wasn’t just following the party line for politicians for the last 30 years.”

More importantly, Carter’s connection to music’s top names far pre-dated his presidential run. As governor of Georgia, he invited Dylan to the state mansion. “When I met Jimmy, the first thing he did was quote my songs back to me,” Dylan says in the documentary. “It was the first time I realized my songs had reached into the mainstream. It made me a little uneasy. But he put my mind at ease by showing me he had a sincere appreciation. He was a kindred spirit – the kind of man you don’t meet every day and that you’re lucky to meet if you do.”

Around the same time, Carter befriended Gregg Allman, whose band had shepherded the huge “southern rock” movement, along with acts like the Marshall Tucker Band and Lynyrd Skynyrd. Together, the bands presented a fresh image for the south, a wave that paralleled the ascent of politicians like Carter, who, in the early ‘70s were heralded as part of the “new south”. In one of Gregg Allman’s final interviews before his death in 2018, he talked about first meeting Carter in Georgia, describing him as “this guy with an old pair of Levi’s with holes in them, no shirt, no shoes,” he said. “I thought, ‘Who’s this bum hanging out at the governor’s mansion?’ That was Jim.”

Still, Carter would never have become more than a figure of curiosity to the musicians were it not for his faith in the power of music to bring people together. His first exposure to that came while growing up in a rural area of the south whose population was 80% Black. “The gospel music of the Black churches was all around him,” said Farrell. “It really resonated with him.”

His own faith had much to do with that. “Music is the closest any of us will get to the divine,” Wharton said. “And Jimmy Carter has always been connected to his spirituality.”

Despite winning the backing of the musicians, Carter’s decision to run for president still seemed a folly at first. “We thought his odds are a little low,” recalled the Allman Brothers’ Chuck Leavell in the film. “But you never know unless you try.”

To make Carter’s triumph even less probable, he wasn’t the only presidential candidate at the time harnessing the influence of rock stars. Governor Jerry Brown of California, who was dating Linda Ronstadt, then at the peak of her popularity, featured her in musical fundraisers along with her friends, the equally powerful Eagles. As a result, some joked that the two politicians were running their own “battle of the bands.”

Yet, only Carter had enough credibility to win over a musician like Nile Rodgers, who had earlier been a member of the Black Panther party. “His campaign made us feel like now we had a candidate who saw the world the way we did,” Rodgers says in the film.

Still, a deeper look into the history of Carter’s politics shows that his public stance on race wasn’t always as pristine as the film presents. In his run for governor of Georgia, he made statements that led many voters in the state to believe he was in favor of segregation, and he did oppose bussing at one point. For that reason, many Georgia voters felt betrayed when he took a strong anti-segregation stance after he got into office. In fact, his first act upon taking office was to hang a portrait of Martin Luther King in the governor’s mansion, which caused the KKK to protest outside the ceremony.

Once he made the leap to the White House, Carter made his feelings equally plain. He offered amnesty to those who avoided the draft during the Vietnam war, an important decision for the young voters who had supported him. His first guest in his new Washington home was Gregg Allman, a risky move since the singer was, at the time, facing a cocaine possession charge. (He got out of it by testifying against his supplier). “Everyone told Carter to distance himself from Gregg,” Wharton said, “but he stood by his friend.”

Carter’s loyalty underscored his allergy to judgment, a key part of his expression of Christianity. “His isn’t the evangelical, fundamentalist view,” Farrell said. “He had a purer view of what Christianity meant.”

Carter had an equally clear view of the complex connection between music and race. During the Jazz on the White House Lawn concert he hosted, featuring stars like Dizzy Gillespie and Sarah Vaughan, “he talked about this great American art form where, for a long time, black and white musicians were not able to play together,” Farrell said. “He called it out as racism. In 1978, to hear Jimmy Carter say that was incredible.”

Despite the wave of hope that ushered Carter into the White House – and regardless of his achievements in office, including the Camp David accords between Israel and Egypt – his administration was overshadowed by runaway inflation, gasoline shortages, and most ruinously, the Iranian hostage crisis. All that helped make him a one-term president, losing to Ronald Reagan in 1980 in a landslide. “I always thought he got the shortest end of the stick of any president in modern history,” says Nile Rodgers in the film. “When the history books are written, people are going to see him in a very different light.”

Certainly, in the years since he left office Carter has risen to near saint status, buoyed by his work with his foundation. At 95, he remains a strong advocate for public good. Small wonder so many who are quoted in the film talk about how Carter brought back “dignity” and “integrity” to the office, the precise inverse of the most common descriptions of the current occupant of the White House. In a time when young people have become more energized about politics than at any time since Carter’s era, Wharton hopes her film demonstrates to millennials and eligible post-millennials the power they hold. “There’s a lot to be done to work towards the ideals this country was founded on,” she said. “But the only way to do that is to vote.”

• Jimmy Carter: Rock & Roll President is now available in virtual cinemas in the US with a UK date to be announced