Calling Beto O’Rourke’s $38 million dollar fundraising quarter a “record” doesn’t quite do that total justice: O’Rourke, who is challenging Texas Sen. Ted Cruz, raised 30 percent more from July to October of this year than Ohio Sen. Sherrod Brown has raised in all six years of his re-election campaign, and more than Jeb Bush raised for the entirety of his 2016 presidential run.

Within hours of O’Rourke’s campaign announcing his fundraising totals, anonymous Democratic operatives complained to the New York Times about how useful that money could be elsewhere, given recent polls that show him down by 8 points or more to Cruz. O’Rourke’s money, they suggested, would be more valuable to other Democrats in critical Senate races in Arizona, Missouri, Nevada, or Tennessee.

It was a familiar response from establishment figures to an insurgent, progressive Democrat posting huge fundraising numbers: incredulity at how much grassroots donors contributed; skepticism that progressives can win; and a hunger to divert that money to centrist candidates who can’t raise grassroots money themselves.

How’s O’Rourke Raising All That Money?

While raising $38 million in three months is an impressive feat for any candidate, what’s more interesting is how O’Rourke did it: almost entirely online, from hundreds of thousands of people donating small amounts of money, while explicitly turning down money from political action committees. His campaign also actively discourages Super PACs from intervening on his behalf.

This most recent fundraising report saw 44 percent of O’Rourke’s money come from donors giving less than $200 in total, colloquially known as “small-dollar” money. In total, 42 percent of all the money raised by his campaign now comes from small donors. But even that number is a bit misleading because many of the people who gave more than that — and thus, are not counted as small donors — have done so in small increments, their enthusiasm eventually popping through that arbitrary $200 line. His average contribution this quarter was around $47.

O’Rourke’s reliance on grassroots donors further distinguishes his campaign from most congressional races, which by and large rely on a smaller number of donors contributing large amounts of money — even among members of the Congressional Progressive Caucus, most of whom still take corporate PAC contributions. This gives him a big advantage over big money: Very few of his donors have given the legal maximum, meaning that he can — and, according to the new figures, does — go back to those donors again and again asking for more contributions.

Reliance on big donors is a problem that politicians have faced for decades — even for those who want to buck big money. As John Nichols and Robert McChesney recounted in their book “Dollarocracy,” Idaho Sen. Frank Church, a populist campaign finance advocate, wrote in a 1962 New York Times op-ed, “I couldn’t begin to finance my campaign on the offerings of small contributors.”

He was correct, at the time. While Republican operatives like Karl Rove began to find success for party committees in direct mail fundraising in the late 1970s, it was a slow, expensive prospect for candidates to raise money in small amounts up until this century, when digital fundraising allowed small-dollar fundraising to happen at scale.

From the outset of his campaign, O’Rourke made a conscious effort to invest in a digital fundraising operation, knowing that it would be nearly impossible to convince traditional big-money donors to help a Democrat win a Senate race in Texas. In this way, he followed the model of successful small-dollar fundraisers like Howard Dean, Elizabeth Warren, Barack Obama, Bernie Sanders, and Alexandria Ocasio-Cortez.

He hired the digital fundraising firm that ran Sanders’s operation (I was involved in both), and followed the email and advertising staff to their new agency.

O’Rourke has now spent at least $12 million on his digital program, or around 30 percent of all his campaign spending — a huge sum compared to other campaigns, particularly on the Democratic side. The vast majority of that money likely went toward digital advertisements, many of which are designed to grow his email list and get supporters to become donors, but also double as ads that people see (though many of those may be out of state). According to Google’s political advertising transparency report, no other candidate on the ballot this year is spending more money on Google’s platform than O’Rourke. And Facebook’s political advertising tool shows more than 5,300 ad variations run by his campaign.