Sanders went from a long-shot candidate to the head of a national progressive movement in months, and Stein said she believed many of his supporters, turned off by presumptive Democratic nominee Hillary Clinton's record and a bruising primary season, might go Stein's way.
Stein offered condolences to Sanders supporters and praised Sanders for running a "revolutionary" movement that spoke to the issues she also cares about in an interview with CNN Tuesday evening.
"We are here in the event that they feel like they don't have a place to go," Stein said.
Stein, who was also the Green Party's 2012 nominee, said she viewed Sanders as a kindred revolutionary, battling the political establishment. She called Clinton's path to the nomination "a coronation" aided by the media and the Democratic Party.
Stein said that although Clinton and news organizations -- including CNN -- had declared her the presumptive Democratic nominee, it was up to Sanders' supporters not to accept that as the end of their movement.
"If Bernie endorses Hillary, I urge Bernie's supporters not to throw in the towel," Stein said.
Stein slammed Clinton, saying the former secretary of state does not have "a track record that has been good for women and children."
The fact that Clinton has become the first female presumptive presidential nominee for the Democratic or Republican parties did not influence her either.
"We need not just someone who is born with a particular gender identity, but someone in the office who supports women," Stein said, pointing out that she was also a woman and a feminist running for president.
The likely Green Party nominee is pushing progressive positions, including eliminating student debt, cracking down on Wall Street and putting an end to military interventions overseas.
Stein said her campaign had no particular outreach plans set for Sanders' voters because she wanted to be "respectful of the Sanders campaign and his supporters."
She said she had reached out to the Sanders campaign to collaborate in the past many times and that he had never responded. She said that many of Sanders' supporters were instead seeking her out.
"It's very hard having a revolutionary campaign in a counter-revolutionary party," Stein said.