Beto O’Rourke was everywhere, all the time. Jogging through El Paso, skateboarding at Whataburger, passionately defending kneeling N.F.L. players. O’Rourke used social media brilliantly to mount an unexpectedly serious 2018 challenge to incumbent Republican Senator Ted Cruz. But while O’Rourke was the star of the show, a 27-year-old digital producer named Shelby Cole was instrumental in turning the congressman’s toothy charisma into $79 million in campaign cash, most of it donated in small amounts.

Now O’Rourke is poised to run again, this time for president. He will need to repeat the online fund-raising magic on a grander scale, against multiple competitors—and he will need to do it without Cole. She is working for Kamala Harris, whose team watched O’Rourke’s operation carefully. Cole joined Authentic Campaigns, Harris’s longtime digital consultant, two weeks after the 2018 midterms. “Bernie obviously came in with a huge fund-raising number after he announced,” says Keegan Goudiss, who was director of digital advertising for Bernie Sanders’s 2016 campaign and is now an executive at Revolution Messaging. “But I’ve been impressed with what I’ve seen from Harris’s operation so far. Not just that they took in more than a $1 million in the day after she announced. For instance, they understand it can’t just be the candidate doing all the social media. You have to build other characters as surrogates, and they’ve had Harris’s sister and husband out there.”

The competition for key Democratic campaign staff has been ferocious, and it sets the stage for the life-and-death battle for campaign cash that will unfold over the next several months, winnowing the field even before anyone caucuses in Iowa next February. The money primary already seems to have one provisional casualty: Elizabeth Warren. She appears to have made a rookie mistake by hiring a relatively large campaign staff, followed by a sluggish fund-raising start. Her attempt to use the O’Rourke viral playbook—drinking beer in her kitchen live on Instagram—fell flat.

So earlier this week Warren tried to climb from fiscal quicksand to the moral high ground, renouncing events for high-dollar donors and spinning her move as a philosophical statement against the corrupting influence of big money in politics. Her 2020 rivals are scratching their heads. “Everyone at this point is for no PAC money, no super PACs, no oil money, no Wall Street money, no foreign money, and everyone is for overturning Citizens United,” says an adviser to one of the leading Democratic candidates. “It doesn’t strike me as much of a message wedge for Warren to say, ‘Well, I’m not going to rich people’s living rooms.’”

Running for president has always been expensive, but 2020 presents unique campaign fund-raising pressures. Sanders’ success, in 2016, at reaching hundreds of thousands of new, younger, small donors reshaped the game. “Bernie basically funded an entire campaign with online and low-dollar contributions,” says Mark Longabaugh, who was a top strategist for Sanders in 2016. “That has broken the paradigm of bundlers in the major money centers of the East and West Coast.” This time around, Sanders’s opponents are also ramping up low-dollar efforts, partly to enable them to claim they aren’t beholden to corporate influence. Yet the large size of the field—10 declared candidates and counting—means they are aiming at many of the same beleaguered targets. “It’s not like I’m a big fish, but during the midterms I got 75 voicemails asking for money,” the Democratic operative says. “It’s almost like a metaphor for income inequality. The percentage of the population that has the most money is shrinking, so it ramifies what was the big story of the ’18 cycle, the competition in small-dollar fund-raising.”