In a trendy co-working space in Washington, D.C.’s Dupont Circle—where people wear Chucks and fuss about fancy coffee—lies the progressive movement’s empire of political cash. Over the past half decade, Democrats have quietly pulled ahead of Republicans in so-called dark-money spending, funneling hundreds of millions from anonymous donors into campaigns around the country.

The groups that spend money this way tend to have innocuous-sounding names and promiscuously spawn mini-organizations that take up particular state and local causes. The North Fund, for example, spent nearly $5 million trying to legalize marijuana in Montana last year. The Sixteen Thirty Fund—the indisputable heavyweight of Democratic dark money—was the second-largest super-PAC donor in 2020, according to the investigative organization OpenSecrets, giving roughly $61 million of effectively untraceable money to progressive causes. The organization that connects many of these groups—what a critic might call the mothership—is called Arabella Advisors.

Arabella hates this narrative. The organization’s CEO, Sampriti Ganguli, insisted to me that she runs a relatively small business-services organization that does HR, legal compliance, accounting, etc., for clients such as the Sixteen Thirty Fund. Ganguli comes from a consultant background, and she talks like it: Arabella’s mission is to make philanthropy more efficient, effective, and equitable, she told me.

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But Arabella, like the Sixteen Thirty Fund, undeniably benefited from the rush of panicked political giving on the left during the Trump years. As the Sixteen Thirty Fund’s revenue exploded, it spent more money on Arabella’s services—a tenfold increase from 2014 to 2019. And Arabella, as a mission-driven, progressive organization, is caught in a major tension on the left: How can progressive groups justify using billionaires’ money to influence American politics and civic life while earnestly advocating for a wealth tax or political-spending reforms?

“I think a lot about the role billionaires