The pop star joined Clinton on the campaign trail in Iowa and told supporters she's a big fan of the ex-Secretary of State.

"I don't think there's a woman more confident than Hillary Clinton," Demi said, referencing the title of her new album, Confident.

The singer performed the title track at the rally and added she's supporting Clinton's run for the White House, because she believes she's the best person to take over from President Barack Obama following the election later this year (16).

"She completely embodies the concept of women empowerment," she explained.

Clinton revealed she's also a big fan of Demi, who has been open about her struggles with eating disorders and mental health issues, calling her "an extraordinary example for so many in the way that you have talked about issues that people find sometimes hard to talk about".

The politician added, "You've given hope and positive reinforcement to so many. I'm thrilled you're here, lending your voice and your example to our efforts to get people to get out and caucus."

Clinton has built up quite a girl power movement as she battles Bernie Sanders for the Democrat party's nomination for president - Amy Schumer, Lena Dunham, Kim Kardashian, and Katy Perry have also endorsed her, while Sanders has celebrities like Run The Jewels star Killer Mike, Belinda Carlisle and Steve Earle in his corner.