Trump rallies are the centrifugal force driving his campaign. And the campaign has weaponized them to hoover up maximum attendee data.

"Axios on HBO" looked inside the campaign's systematic efforts to gather as much information as possible about attendees — information they hope will supercharge the Trump re-election bid.

Here's how it works: Trump's team has designed the sign-up process — and key parts of the rally buildup — to suck a maximum of information from the people attending. Cellphone numbers are their most prized assets.

The data pitches are beamed from Trump surrogates on the screens outside the venues, from a well-rehearsed warm-up speech by campaign manager Brad Parscale, and from the omnipresent MAGA merchandise stalls inside the rally.

Why it matters: Sources in the Trump camp say they hope to cash in on the base-first strategy that put their candidate in the White House back in 2016. For that to work, they need to know everything about their base. And these rallies may make that possible.

The big picture: The affection between the Trump campaign team and the thousands of people who flock to his rallies is mutual — and strong. In fact, impromptu campsites also spring up around the rallies, as our film crew documented last month in freezing conditions in Manchester, New Hampshire.

And Manchester is no fluke. Trump supporters have also literally pitched their tents for overnight stays before rallies around the country:

Wildwood, New Jersey

Colorado Springs, Colorado

Phoenix, Arizona

"I did it once — it's addictive," one of the frozen MAGA campers told "Axios on HBO." "It's like, I've gotta do another one. Because I've never had the opportunity to express such love. Everybody's in love here."

Team Trump is in love, too.