Sen. Kamala Harris (D-CA) announced on Tuesday that her presidential campaign exploratory committee brought in $1.5 million in the first 24 hours of its existence. It was a massive haul for the first term senator—one that left Democratic operatives, especially those in the digital space, impressed with the savvy of her operation and the political muscle she’d flexed.

But what really grabbed the attention of digital operatives was the work done below the surface.

Harris’ Facebook operation ran a whopping 25,000 Facebook ad variations for its launch, which one operative called remarkable but “overkill.” Through it, they raised money from 38,000 donors (with an average contribution of $37) and expanded her email list by 20 percent.

The more telling stat, however, was what it spent. According to Ian Sams, the campaign’s press secretary, Harris put down more than $100,000 on Facebook ads for the launch. By contrast, Sen. Elizabeth Warren (D-MA) spent $52,574 on Facebook ads during the week of her launch (December 30, 2018 - January 5, 2019); Sen. Kirsten Gillibrand (D-NY) spent $61,765 during the week of her launch (January 13-19); and Rep. Tulsi Gabbard spent $24,600 during that same week. There are no Facebook records for money spent by former HUD Secretary Julian Castro.

“Kamala has been the best by far at this,” said one top operative who is unaffiliated with a campaign currently.

The spending by Harris, strategists say, is a solid sign that her operation is getting a good bang for its buck online—a campaign will spend up to the point that they see diminished rate of returns with respect to email addresses accumulated and dollars raised. It also illustrates the payoffs that her team is currently enjoying for the work it did prior to announcing her bid.

From March 2018 through Jan. 19, 2019, Harris’ Senate campaign spent more than $1.2 million on Facebook ads even though she was not up for re-election until 2022. That money allowed her to build a grassroots fundraising apparatus that Democratic strategists say is third in heft behind only Sen. Bernie Sanders’ (I-VT) and former Rep. Beto O'Rourke's (D-TX). By contrast, over that same time period, Sen. Elizabeth Warren (D-MA) ran $781,000 in Facebook ads and Sen. Kirsten Gillibrand (D-NY) spent $856,000 even though both were running for re-election in 2018.

None of this on its own is predictive of a successful campaign, operatives stress. Others have yet to get into the race and as an aide to Castro noted, their campaign (like others) isn’t expected to match fundraising totals with those who have had prior Senate campaigns.

“We’re starting from scratch but we expect to grow exponentially as we get Castro’s message out,” the aide told The Daily Beast. “We are declining all PAC money and donations from lobbyists. Don’t write us off because we didn’t raise $1.5M in a day. Our race is a marathon, not a sprint.”

But the surest tell that Harris’ launch was more seamless than the others was in the fact that no other candidate revealed their 24-hour fundraising haul. Warren’s campaign declined to do so and Gillibrand’s campaign didn’t return a request for that number

Uncommitted operatives are keeping close tabs on the way these rollouts are progressing. And the impression is that Harris’ operation has been both crafty and dogged at using online tools. The senator has used an email fundraising style that accentuates the personal aspects of running as opposed to dire warnings in subject lines. The former can help build a loyal and devoted list of small-dollar donors while the latter may raise quick cash but can compel individuals on the list to disengage.

The Harris campaign has already cited the success rate of an early email that employs the behind-the-scenes style that became hallmarks of Sanders’ 2016 presidential bid and, more recently, O’Rourke’s Senate campaign. As part of the data made available to reporters on Tuesday, Harris’ campaign said that a personalized email co-written by Harris’ husband Doug raised six figures for the campaign within the first few hours it was sent out. It featured pictures that he had taken throughout the day of Harris’ announcement and was co-written by Shelby Cole, a digital staffer who had worked on O’Rourke’s campaign.

“One philosophy is you raise the most money by playing the long game. You bring people into the fold,” an uncommitted operative told The Daily Beast of this strategy. “If you inspire them over time, they’re going to give you a lot of money.”

While Harris has impressed operatives with the professionalism of her rollout, others note that there is time and space for fellow Democrats—and those not yet even in the race—to make their own imprint. Everyone who has entered the race so far has announced their candidacies in traditional mediums: a book tour, a late-night television appearance or an impromptu CNN interview. Left untapped is a campaign launch that is distinct in its use of new digital tools, such as video live-streaming or a direct announcement via a Facebook page.

One operative speculated that if O’Rourke gets in the race—something that is so far undetermined—he might do a Facebook live announcement, especially given his meandering Medium posts about his travels in the past few weeks. Sanders could opt to do the same given the size of his online following. Both, strategists predict, would likely be able to pull in sums of money similar to or even larger than Harris.

"They definitely have big social audiences for sure that would tune in any time,” the operative told The Daily Beast.