Bernie Sanders may have been dubbed an outsider candidate in the 2016 presidential election, but the Democratic candidate's progressive agenda has been shaping American politics for nearly four decades. In his presidential campaign, the 74-year-old senator from Vermont has reached millions of Americans with the same populist message of wealth inequality, which the filmmakers behind the new documentary Bern: The Movie hope will prevail, with or without Sanders winning the party's nomination.

“This film came about for a couple of reasons. One, because I’ve always been politically active, mostly because I like making positive change, and two, I saw the energy and enthusiasm surrounding Bernie Sanders and knew it was something I wanted to be a part of," says executive producer Jay Matthew in the film's introduction.

The film tracks Bernie Sanders' life from student activist to Burlington mayor to congressman to presidential candidate, and the movement he has shaped along the way. One of Sanders' most lauded accomplishments in the 2016 election is self-funding his campaign on individual donations averaging $27 each. And those same contributors not only funded this film, some of them even starred in it.

“I have always been a fan of Sanders," Jay Matthew told AlterNet. "He really sealed the deal for me when he was the keynote at the California Democratic Convention in 2010…. The rest of the crew liked him but did not know much about him when we started."

Like many Bernie Sanders supporters, Matthew has great respect for Sanders' consistency.

"If you just listen to the audio from the sneak peek, without looking at the footage, you would be hard-pressed to be able to tell when he said it. Was it yesterday or 30 years ago? That is extremely rare in a political candidate. And on top of that, the struggles he faces while growing up mirror so many people today here in the United States. He has a fascinating history that I think many people can relate to," Matthew said.

What would Hillary Clinton have to do to sway the "Bernie or Bust" crowd in a general election?

"I think she and Bill have made it pretty clear they are not really that interested in doing anything to win over Sanders' supporters. Which I find troubling," Matthew said. However, the producer is "interested to see if such a scenario plays out."

"Bern: The Movie" premieres on May 27.