She’s a medical doctor and former Democrat.

She has plenty of experience on the political stage, but it hasn’t always been successful.

She’s pretty similar to Bernie Sanders — but more intense.

While Donald Trump and Hillary Clinton are the biggest names in the presidential race, they're not the only candidates running. Other parties are putting their own candidates forward, too. Enter Jill Stein, who's running for the nation's highest office on the Green Party's platform. Stein announced her candidacy back in 2015, but her bid appears to be picking up some momentum in the wake of Bernie Sanders' exit from the Democratic primary. Some Sanders supporters have since flocked to Stein and, according to a recent CNN poll , she and running mate Ajamu Baraka currently have a solid 5% of the prospective vote — no small feat for a third-party candidate. So, who is Jill Stein? Here's what you need to know about the White House hopeful.A graduate of Harvard Medical School, Stein spent decades practicing internal medicine before she became involved in politics, making the transition based on the health effects of the environments people live in. Stein started her political career as an environmental activist, advocating to shut down coal plants in Massachusetts in the late 1990s. From there, she turned to addressing the issue of campaign finance reform — an issue which eventually pushed her away from the Democratic Party when, as she told NBC in March, the party “killed” campaign finance reform in Massachusetts. Despite her medical expertise, Stein was criticized in July for comments that seemed to imply that vaccines were unsafe. In a Reddit "Ask Me Anything" in May, she suggested that the regulatory systems that approved vaccines were unreliable because of corporate influence by the pharmaceutical industry. But she also declared her support for vaccines in a July interview with The Washington Post , when she said that “there were real questions that needed to be addressed” regarding vaccines during her time as a physician, but that they were an "invaluable medication," too.Stein was elected to the town board of her hometown, Lexington, MA, in 2005, and then re-elected in 2008. But she has more experience losing than she does winning. She lost a bid for Massachusetts state representative in 2004, as well as a 2006 campaign for secretary of the commonwealth. She ran for governor of the state twice — in 2002 and 2010 — and lost both times. But it didn’t stop her from continuing to run for office. Stein was the Green Party candidate in 2012, where she brought in nearly 470,000 votes , or about 0.36% of the overall vote. As of right now, she holds the record for most votes for a female candidate in the general election, making her the most successful woman to have run for the presidency according to Time.Stein’s platform has a lot in common with that of the now-defunct Sanders campaign . Like Sanders, Stein is adamant about addressing climate change, campaign finance reform, and income inequality. But she tends to take the stances further than the Vermont senator ever did, as evidenced by her position on student debt. Stein supports, not only making higher education tuition-free , but actually forgiving the debt of those who have already been through the system, according to her Reddit AMA. She also supports far-left causes like a guaranteed minimum income and a full transition away from fossil fuels and towards renewable energy by 2030. The similarities are enough that Stein has a realistic hope of pulling in disillusioned Sanders supporters who may prefer her to Democratic nominee Hillary Clinton. A Bloomberg poll in mid-June showed that only 55% of former Sanders supporters have turned to Clinton since she became the presumptive nominee.