Washington (CNN) There's an independent senator -- a democratic socialist, no less -- with climate change on the brain making a real play for the Democratic nomination against Hillary Clinton, who exudes establishment politics.

What's the Green Party, which has been railing against the Democratic Party for years, to do in the year of Bernie Sanders?

For Jill Stein, 2012 Green Party presidential nominee and current candidate, the answer seems to be keep on going.

"Forward movement is a good thing, but I always include that it's not enough, and we have to have a base where we can truly build," Stein told CNN. "That cannot be done inside of the corporate, establishment political parties."

Stein's third party bid for the presidency is centered on student debt, climate change and opposition to the economic and political establishment -- also focal points for the Sanders campaign, a similarity Stein readily acknowledged.

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"I think we share very similar values and visions," Stein said. "I just happen to be working in a party that supports those values and those visions."

Sanders has made changing the Democratic Party a key pitch to his voters. Stein's disdain for the Democratic Party is key to hers.

"I have long since thrown in the towel on the Democratic and Republican parties because they are really a front group for the 1%, for predatory banks, fossil fuel giants and war profiteers," Stein said.

Stein had many positive words for the Sanders campaign but said he was constrained by a political party with a history of coopting progressive campaigns.

"The party allows progressive faces to sort of be their figurehead for a little while, but while it does that, while it sort of fakes left, the party continues to march toward the right," Stein told CNN.

Stein said the Democratic Party, along with the Republican Party, represented corporate interests and has not allowed progressives to take charge. The story she told of the Democratic Party was one of a party that had used its "kill switch," in the form of packed primary days, like Super Tuesday, and super delegates, to take down "very good and principled campaigns" over the decades.

These progressive campaigns "are invariably sabotaged by the (Democratic) party," she said.

She cited the Democratic Party's changing of nomination rules following George McGovern's 1972 bid as well as the failures of Jesse Jackson, Howard Dean and Dennis Kucinich. She predicted a similar fate for the Sanders campaign, which she said had nevertheless "elevated the debate enormously."

"I think the Democratic Party is going to cut them off at the path, and then maybe it will fall to our campaign to be the Plan B for Bernie's supporters," Stein said.

In 2012 when Stein last ran for the presidency, she garnered almost 470,000 votes , or .36 percent of the popular vote, according to the FEC. The Green Party's high water mark was Ralph Nader's 2000 run, where he got nearly 3% of the vote nationwide.

'No response' from Sanders

Although she split with Sanders on a number of major issues, she welcomed the opportunity for the two candidates to collaborate.

"The Green Party has been trying to contact Bernie Sanders since 2011 through emails, paper letters and phone calls," Stein said. "We approached him about a potential collaboration in 2012 race and again before this race actually."

Stein said her invitations to collaborate have received "no response whatsoever" from Sanders.

"He's a team player, and he believes in the Democratic Party, so I have to respect that," Stein said. "He believes in the establishment, in the political establishment. He's been in Washington a long time. He caucuses with the Democrats."

The Sanders campaign did not respond to multiple requests for comment on this article.

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Stein said she does not believe the Democratic Party can or will bring about the kind of revolution she, and Sanders, have called for.

"It (the Democratic Party) hasn't been winning for the agenda that Bernie Sanders supports, but he's very afraid of splitting the vote," Stein said.

By "splitting the vote," Stein was referring to a belief she said many Democrats have that third party candidacies bolster those they most oppose. For example, some said Ralph Nader, who ran as the Green Party candidate and got 2.74 percent of the vote, helped George W. Bush defeat Al Gore in the 2000 presidential election -- an assessment Nader rejected

Stein said any worry over a potential third party spoiler effect could fixed through voting reform.

"We could fix that in the blink of an eye with a simple voting reform called rank choice voting that allows people to rank their choices," she said.

Although she welcomed collaboration with Sanders, she had few positive words for Democratic front-runner Hillary Clinton.

Asked if Clinton was, in her view, a progressive, Stein laughed and said, "No, not in the least. This is Goldman Sachs' best friend."

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Stein offered a litany of Clinton's failures to live up to the Green Party's standards, from the former secretary of state's Wall Street speeches to her record on foreign policy, international trade, fracking and many other issues.

"In what way exactly is she progressive?" Stein asked.

"There's a very long and consistent track record on the part of Hillary Clinton, and it's not been favorable to women, to children, to the cause of peace, justice and a sustainable climate," Stein said.