Miami (CNN) They will not share a debate stage this week, but that distance is unlikely to cool one of the most intense competitions brewing inside the Democratic primary -- between Sens. Elizabeth Warren and Bernie Sanders, who are tangling over who will emerge as the most electable liberal champion.
As Warren promises big ideas, imploring supporters to "dream big and fight hard," Sanders is urging his own supporters to push for a revolution, pledging "to complete what we began." But this time around, he has considerable competition in his pursuit of progressive voters.
And while their broader policy ideas are similar, including their calls to implement "Medicare for all," pass provisions of the Green New Deal and fight income inequality, there are key differences.
Sanders unveiled a proposal this week to wipe out all outstanding student debt in the country, while Warren's plan implements means testing. She proposes to forgive up to $50,000 for anyone in households making less than six figures a year. It's a subtle but key distinction beginning to frame their dueling candidacies. But loyal Sanders supporters said the biggest difference with Warren is the breadth and depth of his movement.
"Sen. Sanders is not just trying to win the race, he is trying to create a revolution," said Nina Turner, a co-chair of the Sanders campaign. "There's a difference between, as somebody put it, pushing regulations and creating a revolution. And the revolution says that I want to bring millions and millions of people with me so that movement can sustain itself beyond the candidate."
Warren is not only stealing a share of Sanders' thunder but she's also attracting some of his admirers, who see her as the fresh face of the left who many believe may be more electable.
"I am a strong supporter of Bernie Sanders too, but what I love about Elizabeth Warren most of all is her ability to reach across and talk to people in a different way," said Regina Bailey, a South Carolinian who is now supporting Warren. "It's not as upsetting to other people. I think it would be able to bridge the gap and to be able to sway other voters more so than Bernie Sanders."
Bailey paused for a moment as she said the word "upsetting," later explaining she isn't turned off by Sanders' rhetoric, which can seem strident to some, but that she thinks some voters are. Her views, she said, are also shaped by her belief that it's time for a woman to reach the Oval Office.
"I voted for Hillary Clinton. I definitely would like to see, in my lifetime, a female president. I'm not going to lie to you, I would like to see that," Bailey said. "I think it's time for an intelligent woman to lead the country."
One of the sharpest differences between the candidates, which is increasingly playing out on the campaign trail, is Sanders' embrace of Democratic socialism and Warren's often-expressed support for capitalism. That viewpoint has made her candidacy far more appealing to moderate Democratic groups like Third Way, which has never favored Warren but thinks she is far more preferable than Sanders.
For his part, Sanders is making clear that he feels footsteps, suddenly painting Warren as more of an establishment candidate. The Vermont independent made that argument the theme of his weekend speech at the South Carolina Democratic convention, declaring: "I was called an existential threat to the Democratic Party."
He didn't mention Warren, but the subtext was clear. When asked whether he was just displeased at Third Way's support of the Massachusetts Democrat, he snapped: "I don't care who they prefer. That's not what I'm talking about."
But in a field of two dozen candidates, Sanders and Warren still sit on the same side of the spectrum. They insist it's a friendly completion.
"I think Bernie is terrific," Warren says when asked about Sanders. "We were friends long, long before I ever got involved in politics."
When he's asked, he often offers this reply: "Elizabeth is a friend of mine. I think she's running a good campaign."
Yet just beneath the surface, tensions are rising. Some Sanders supporters have never forgiven Warren for endorsing Hillary Clinton in 2016 after the primary contests but before he had formally dropped out of the race.
As Warren rises in polls, both nationally and in early-voting states, the chatter from loyal Sanders followers has grown sharper. In online forums, Sanders supporters raise questions about Warren's electability, pointing to the controversy over her claimed Native American heritage, which once threatened to consume her candidacy.
Warren aides say they are bracing -- and preparing -- for a fight to be the progressive alternative. Sanders advisers express admiration for Warren but point out that his ideas are driving the 2020 conversation.
"People have to decide do they want originals or do they want copies," Turner said. "He's the original."