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Denver (CNN) -- While an increasingly unpopular President Obama seems to be on a self-imposed Rose Garden strategy this election, one Democrat is in demand on the campaign trail: Sen. Elizabeth Warren.

She's an unabashed progressive from Massachusetts, a Democrat who thinks Democrats are too timid and a populist who has been called to help in red, blue and purple states. And despite her frequent protests, she's someone that liberals long to see launch a 2016 bid for the White House.

Warren is an unusual Washington phenom—a combination of loyal soldier and inside agitator, a star who has no problem taking on her own party.

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"What the Democrats have to do is be willing to stand up and fight," she tells CNN. Asked if the party hasn't been willing to do that, she responds: "I just think we can use a little more of that. I think we can use a little more of standing up and saying this is what it's about, and I'm willing to do it."

Warren's job this election season is to gin up a party base that lacks energy, and she's been taking her message to get out the vote to 15 states so far. This weekend, she ventures to New Hampshire to stump for Sen. Jeanne Shaheen, locked in a close contest with Republican Scott Brown. The race is personal for Warren: she defeated Brown in 2012 for her Senate seat when he lived in Massachusetts.

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Warren has also raised money -- about $6 million -- for the party this cycle.

But most of all, she's reminding Democrats that they have a large stake in this election.

"The powerful and the rich should get richer and more powerful," Warren tells a crowd of several hundred in Boulder. "That's what it's all about for the Republicans."

Warren is the messenger that President Obama can't be—at least not now. It's been a tricky election year for him: his popularity is on the decline, the world is increasingly dangerous and his Democrats are at growing risk of losing control of the Senate. They're left in a precarious place, trying to figure out the best ways to motivate the Obama base -- without Obama.

Enter Warren.

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In Colorado, where incumbent Democratic Sen. Mark Udall is in a tight race against Republican Rep. Cory Gardner, she plays to the college audience in Boulder.

"The fight comes to you. If you pick up what you've got, and you put everything you can into it, then together you, me, Mark, all of us, that's how we are going to build a future together," she says.

But she's also been able to play in the red states of West Virginia and Kentucky, where she campaigned this summer with Senate candidates Alison Lundergan Grimes and Natalie Tennant.

Warren's rise as a party star is, well, complicated.

While the president first tapped her to help create the Consumer Financial Protection Bureau, he did not nominate her as its first chief—worried she could not get confirmed--so she ran for the Senate, with White House backing. But she's not shy about taking on the White House, calling its bailout more of a sell-out.

"You know if President Barack Obama had not been in the White House we would not have the Consumer Financial Protection Bureau today. This is an agency that has forced the biggest banks in this country to return more than four billion dollars directly to people they cheated, and that's been just three years," she tells CNN.

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But there's a but in there: "Of course there's a but coming because there's another half to this...He also chose an economic team and when the going got tough, the economic team chose Wall Street. They protected Wall Street over American families, and that's just something I think is fundamentally wrong."

In the past, she has also called former Secretary of State Hillary Clinton— a frontrunner for the 2016 Democratic presidential nomination and an ex-New York senator--too close to the financial sector.

"I have said I worry about everyone who is too close to Wall Street. When I describe what this race is about, it's about who does government work for. I worry everywhere," she says in the interview.

Not exactly a ringing endorsement, although she has signed a letter urging Clinton to run for the presidency. Even so, she has become the left's anti-Hillary and the Republicans poster child for big government liberalism. She and her agenda star in the conservative PAC American Crossroads videos linking her to Obama.

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Republicans say she energizes their base as much as she does the Democrats, but she balks at the notion.

"Whoa, whoa, wait, wait because I believe we should have a little higher minimum wage, because I believe women should have access to birth control, because I believe the United States government not be making tens of billions of dollars in profits off the backs of our kids on student loans, because I believe Social Security should not be privatized. That's what I believe in. That's what I am out there fighting for."

She's fighting, she says repeatedly, to keep Democrats in charge of the Senate in 2014.

But what about 2016? She is determined not to look beyond this year's election, staying relentlessly on message while her supporters want the 2016 door open: "You could ask this as many ways as you want. I'm not running for president."

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