Thousands of people packed under the marble arch of Manhattan's Washington Square Park to hear Elizabeth Warren on Monday. They didn't show up by accident.
The crowd was the product of a carefully planned, data-driven strategy to identify supporters, attract them to a rally and ultimately convert them into voters, a plan that goes well beyond producing a compelling scene for television.
In an era where campaigns increasingly try to leverage technology to tactical advantage, the attention to detail by Warren's team stands out. Like other candidates, before an event, her campaign invites past donors and other likely supporters who live nearby using email, mass text alerts and "peer-to-peer" text messages that staffers write to individuals.
But that's just the start. At the venue itself, attendees must line up and check in using their phones, even if they've previously RSVP'd. When finished, they're sent a picture of the senator's golden retriever, Bailey, which they show at the door to be issued a red-dot sticker proving they've complied.
Warren's campaign spent months testing how best to collect information, trying out things like different colors of paper signup sheets before settling on the current system since attendees get a doggie picture they're likely to enjoy.
"It's efficient but also fun," said Tessa Simonds, the Warren campaign's director of grassroots mobilization.
Warren has mastered the art of drawing thousands to her rallies, but, more importantly, those turning out are also a proxy for her recent rise in the polls. And the crowds have been building for weeks in places that have received relatively little attention from other candidates, including Seattle,
In 2016, the enormous crowds who flocked to see Bernie Sanders were an early sign of the enthusiasm that would build around his campaign and lead him to nearly defeat Hillary Clinton for the Democratic nomination. This cycle, Sanders and other Democrats have also staged large rallies, but it is Warren who seems to hold the energy edge.
Trump's large crowds four years ago hinted at his coming Election Day upset. Similarly, Barack Obama was still largely unknown nationally when he launched his presidential bid in 2007 — yet demonstrated his early strength by drawing 20,000 at a Super Bowl Sunday rally in Delaware.
"When you get a big crowd and reporters are covering that and they're like, 'Wow, there's a lot of energy in the room,' ... that can absolutely get you free earned media," said Brendan Steinhauser, a Republican strategist and former top conservative grassroots organizer. "And if we learned anything from 2016, earned media is really valuable and can — pardon the pun — trump the paid media."
Big crowds aren't everything, of course. Many Democrats bitterly remember throngs watching Clinton, Bruce Springsteen and Jon Bon Jovi in front of Philadelphia's Independence Hall the night before Trump's 2016 victory. Democrat Walter Mondale attracted massive 1984 crowds in New York and Boston days before losing 49 out of 50 states to President Ronald Reagan.
That's because large rallies can show enthusiasm but often aren't good indicators of whether support is growing beyond a candidate's established base. The people who show up to such events tend to be self-selecting.
"It's all reinforcing, the data, plus the visuals on TV feed more people in the crowds," said Joe Trippi, campaign manager for Howard Dean, who organized early rallies large enough to briefly become a 2004 Democratic presidential primary front-runner.
But when voting began, it became clear that the former Vermont governor was more effective at building ballyhooed crowds than winning votes.
"The issue is going to be, all that buzz on television and online, and the resources that it gets you, does that expand beyond that base support?" Trippi asked. "In the Dean campaign, it didn't. In Obama's it did."
Judging crowd size is subjective, meanwhile, and can be so politically charged that police sometimes refuse to offer official estimates.
Warren's campaign says its crowd-size estimates partially come from staffers and volunteers using counting clickers to gauge the number of attendees. It estimated the Manhattan attendance at 20,000-plus, and staffers said that more than 5,000 people heard their candidate last week in Austin — despite thunderstorms blowing in earlier in the day.
Speaking to reporters on Tuesday, Trump said of Warren's New York crowd: "Anybody can do that."
"No. 1, she didn't have 20,000 people," the president said. "And No. 2, I think anybody would get a good crowd there."
The Warren campaign won't discuss its "targeting" of would-be supporters or such analytical components like how many people it has in existing nationwide donor, volunteer or supporter lists. Aides concede they hope anyone invited to rallies will increase turnout by bringing friends, neighbors or relatives, but refuse to quantify how many new attendees such scenarios tend to generate.
Still, attracting the crowd is only the beginning.
Warren volunteers are trained as "canvassers," asking event attendees to rank their top three Democratic presidential primary choices. The campaign won't say if it treats people leaning toward other candidates differently from avowed Warren supporters.
Todd Beach, a 49-year-old warehouse clerk, came to Warren's Austin rally but said his first choice in the primary was former Texas Rep. Beto O'Rourke.
"The crowds are great, but that doesn't impress me," he said of Warren. "What matters is the content of the speech."
Betting many will like what they see, though, Warren staffers follow up with rallygoers quickly, issuing text or email solicitations for donations or future volunteering — sometimes during or immediately after the event.
In states where Warren's campaign has lots of staffers, like make-or-break Iowa, large teams of organizers can easily make follow-up contact. In other places, including Austin, staff based at Warren's Boston headquarters travel to the area beforehand, hoping to convert rally attendees into future volunteers.
Warren spends hours after each event taking selfies with attendees — and her staffers and volunteers work those lines, too, looking for future volunteers or people willing to try to recruit friends and neighbors to be supporters.
Sometimes Warren herself pitches in.
Nolan Screen, a 19-year-old student at Austin's St. Edwards University, waited about half an hour for a picture with Warren and told her that he was trying to learn as much as possible about the political process before casting his first presidential ballot. Warren said she'd be there for advice and suggested he send her a direct message on Twitter.
Screen has no social media presence, but said afterward he "may create a Twitter account now."