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The Democratic primary campaign sometimes seems like a big, sprawling mass of candidates - 23 at the latest count. But inside that scrum are some intramural contests, like the so-called progressive primary, which has two main candidates, Bernie Sanders and Elizabeth Warren. Here's NPR's national political correspondent Mara Liasson.
MARA LIASSON, BYLINE: Eight months before the Iowa primary, the polls show Joe Biden in the lead. Behind him in second and third place are two progressive giants, Senators Bernie Sanders and Elizabeth Warren.
BILL PRESS: I was a big Bernie supporter in 2016. And in fact, the Bernie campaign was housed in our living room.
LIASSON: That's Bill Press, former chair of the California Democratic Party. This year, Press is not supporting anybody. Like other progressives, he's watching Warren and Sanders to see how it plays out. Right now, Sanders has some obvious advantages. He has universal name ID among Democrats because he ran in 2016, and he has a massive and devoted small donor base. But Warren also has strengths. For most Democrats, she's a fresh face. And, says Press, she's a policy machine.
PRESS: Nobody's put out more substantive policy proposals than Elizabeth Warren. It's almost one a day. I mean, the Electoral College, the wealth tax, breaking up the big tech companies, climate change. She's added a lot of new, very bold progressive proposals, whereas I think Bernie to a certain extent is oldies but goodies.
LIASSON: At this early stage of the race, supporters of Warren and Sanders are reluctant to criticize the other candidate, but they both describe their candidate as more electable, the quality that's top of mind for Democrats this year. California Congressman Ro Khanna is backing Sanders.
RO KHANNA: I think he really can help the Democrats win back areas that we need to and help stitch this country back together. Ultimately, I believe Bernie Sanders will win because Bernie Sanders' vision of getting us out of bad wars, of having fair trade, of having "Medicare for All" is more consistent, not just with what the Democratic Party wants, but what the country wants.
MARIA URBINA: I think they're both progressive champions.
LIASSON: Maria Urbina is the national political director of Indivisible, a network of grassroots activists which has not endorsed a candidate this year. But Urbina says her members are paying close attention to the way both Sanders and Warren present themselves on the campaign trail - how Sanders tries to expand his coalition to include more people of color, how Warren connects her policies to the people she meets.
URBINA: She's gone to 20 states, has done 50 town halls. And the more that she hears from people and the more that she talks to people, folks are really excited. And that's what you're seeing a lot of these grassroots movement leaders react to.
LIASSON: Warren's town hall appearances and endless selfies with supporters have generated a lot of buzz and a little upward movement in the polls. Both Warren and Sanders are talking about big systemic change. They both say they want to make the American economy and political system work for everyone. But there are important differences. Warren believes in markets, the fundamental building block of capitalism. She says she wants markets to have real rules that everyone follows to create a level playing field for workers and consumers.
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ELIZABETH WARREN: And as long as we've got that then we will get the best out of markets because it means the people who come up with great ideas, who work hard, are the ones who will prosper, not simply those who were born into wealth.
ED O'KEEFE: So if you get labeled as a socialist...
WARREN: Well, it's just wrong.
LIASSON: To CBS's Ed O'Keefe, Warren explicitly rejected the socialist label. Sanders, on the other hand, proudly identifies himself as a democratic socialist.
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BERNIE SANDERS: Are you ready for a political revolution?
LIASSON: Restructure capitalism or rip it up by the roots. That's a real ideological choice, says Bill Press.
PRESS: Elizabeth Warren is more of the reformer than Bernie the revolutionary, meaning one who sees making our existing system of government work better to serve all Americans. Whereas Bernie is more - at least the message is more - blow it up.
LIASSON: How their competition resolves itself may do more than just help determine the outcome of the Democratic presidential primary.
PRESS: I think it's a battle for the heart and soul of progressives. It's important because it will decide in many ways the direction of the Democratic Party.
LIASSON: And that's why primary campaigns matter. In addition to choosing a standard bearer, they can also help shape the character of the party. Mara Liasson, NPR News, Washington. Transcript provided by NPR, Copyright NPR.