Hillary Clinton takes aim at Trump as she brings her life story to Sundance

Hillary Clinton has returned to the political stage at the Sundance film festival with a vow to work to defeat her Republican antagonist Donald Trump in November.

"Hillary," a documentary about the former Democratic standard bearer, was screened at the prestigious festival Saturday ahead of its world premier.

Due to air in March as a four-part series on streaming site Hulu, it already has made waves in a turbulent election year.

Clinton's caustic remarks in the documentary about Senator Bernie Sanders, her rival for the Democratic nomination in 2016 and now a frontrunner in the current race, received wide play in the US media, not all of it favorable.

At the festival, though, Clinton kept her focus on Trump, whose shock victory a little over three years ago stunned the country and cut short her seemingly unstoppable political ascent.

"I just think we have to win. I don't think we can afford another four years by the current incumbent," she told reporters.

"I think that would be absolutely dangerous to our democracy, and I'll do whatever I can to make sure the Democrats win this time," she said.

Backed by a phalanx of security unusual for such events, the former secretary of state and first lady extended her remarks in a clutch of red carpet interviews.

"We have to be better than the other side, because they are highly organized and incredibly well funded, and they have foreign help," she told AFP.

"We should win, because I think people can see the broken promises and the failed actions of this current administration," she said.

"And so we should win, but we're gonna have to overcome all of the obstacles they are throwing our way," she said.

After a period of relative quiet for one of America's most formidable political actors, Clinton's blistering remarks about Sanders announced she was back.

"Nobody likes him, nobody wants to work with him, he got nothing done. He was a career politician.

"It's all just baloney and I feel so bad that people got sucked into it," she said.

She refused to take her comments back, but later said she would support whoever becomes the Democratic nominee. Sanders has since surged into first place in polling in Iowa, the first state to vote in the Democratic nominating process, on February 3.

"The point of the documentary is what a polarizing figure Secretary Clinton is," Nanette Burstein, who directed "Hillary," told AFP.

"She is both admired and vilified, and the whole top line of it is to break that down. So I had no illusions that in the reaction to this piece, it would be the same thing," she said.

Burstein was nominated for an Oscar in 2000 for "On the Ropes," a documentary about three young boxers and their trainer.

The Hillary project began as a behind-the-scenes look at the candidate's 2016 campaign, relying on some 1,700 hours of footage taken by Burstein's team.

But as it progressed, the documentary's producers changed tack.

"They came back and they said, 'You know, there's a bigger story here, and we want to tell your life, and we want to talk about the arc of women's lives and politics," Clinton said.

"I said, 'Sure, let's do it.'"

"I figured, let's tell our story, because we've got to do more to get people to understand what's going on in our country and the world, and if this can contribute to that, I'll be very happy," she said.