The group's 2018 fundraising surpassed any amount ever raised by a left-leaning political nonprofit, according to experts, who pointed to the Koch network and the Crossroads network as rare right-leaning groups that posted bigger yearly fundraising totals at the height of their powers.

The Sixteen Thirty Fund’s rise last year is a sign that Democrats and allies have embraced the methods of groups they decried as “dark money” earlier this decade, when they were under attack from the money machines built by conservatives including the Kochs.

“In terms of the size of dark money networks, there are only a few that have gone into the $100 million-plus range,” said Robert Maguire, the research director for the watchdog group Citizens for Responsibility and Ethics in Washington and an expert in political nonprofits.

“These kinds of totals aren’t unheard of,” Maguire added. “I do think they’re unheard of on the liberal side. I think that’s what’s so striking about this.”

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In an email, Sixteen Thirty Fund executive director Amy Kurtz wrote that the group “provides support to advocates and social welfare organizations around the country, and we are pleased with the growth we had in 2018.”

Sixteen Thirty Fund played a role in the battle for the House of Representatives in 2018, a crucial contest for Democrats trying to seize back power after Trump’s rise. The election featured dozens of Democratic candidates who decried the influence of money in politics on the campaign trail.

The nonprofit operated under four dozen different trade names in 2018, many of which have benign-sounding local titles like Arizonans United for Health Care and Floridians for a Fair Shake. POLITICO revealed in 2018 that a number of these linked groups were collectively spending millions of dollars to pressure Republican members of Congress on their stances on health care, taxes and the economy through TV ads and grass-roots organizing.

A related organization called the Hub Project controlled the flow of money for this effort from Sixteen Thirty Fund into states and districts, according to reporting by The New York Times. This year, the group is “continuing to work on campaigns that Americans care about,” Hub Project spokesman Dan Crawford said, including campaigns focused on health care, taxes and the economy.

Demand Justice, the courts-focused group helmed by former Hillary Clinton press secretary Brian Fallon, also ran out of Sixteen Thirty Fund. Demand Justice spent millions of dollars on TV ads as Democrats tried to prevent Brett Kavanaugh from being confirmed to the Supreme Court in 2018. More recently, the group projected a video of Christine Blasey Ford accusing Kavanaugh of assault on the side of a truck outside a Washington gala where Kavanaugh was speaking.

In addition to the direct spending conducted under prominent trade names, Sixteen Thirty Fund also distributed more than $91 million in grants to 95 other groups in 2018, according to the tax filing. These funds made Sixteen Thirty Fund a major source of money for political nonprofits pushing an array of changes to state and federal law.

More than $27 million of that money went to America Votes, another liberal nonprofit that describes itself as “the coordination hub of the progressive community” on its website. That grant by itself was nearly twice the amount America Votes had ever raised in a single year ($14.2 million), according to federal tax records.

Sixteen Thirty Fund also directed tens of millions of dollars directly into state-level politics, including a series of successful ballot measures. The group gave $6.25 million to a group urging passage of a Nevada ballot measure promoting automatic voter registration, as well as $6 million to a Michigan group pushing changes to the state’s redistricting process. Another $2.65 million went toward boosting a Florida constitutional amendment restoring voting rights to felons. Groups pushing minimum wage increases in Arkansas, Missouri and other states received millions more.

More than $10 million flowed from the Sixteen Thirty Fund into Colorado alone, to organizations supporting Democrats in state legislative races and campaigns for statewide office, as well as several more focused on expensive ballot measure campaigns.

“The ballot initiative process offers an important counterbalance to the failings of partisan politics and we are proud of our support for some of the most impactful and important initiatives of the 2018 cycle,” Kurtz, the Sixteen Thirty Fund executive director, wrote in an email.

The group does disclose the amount of money of each donation, which shows several strikingly large contributions: One donor gave the group $51,705,000; a second gave $26,747,561 and a third gave $10,000,000. And The Hub Project disclosed three of its donors in 2017: Seattle venture capitalist Nick Hanauer, the union American Federation of Teachers and the Wyss Foundation, founded by businessman and environmentalist Hansjörg Wyss.

The huge size of Sixteen Thirty Fund and its donations raise questions about whether it has its own independent base of donors or if whether acts as one part of a larger network, said Brett Kappel, campaign finance lawyer at Akerman LLP.

“When you see a very large contribution — which is more than a third of the money raised — that raises the possibility that other groups are funneling money to this group to distribute to individual states,” said Kappel. “Is this part of a dark money network? And what’s its function?”

There are some signposts that partly show Sixteen Thirty Fund’s operators and potential sources of its funding. Sixteen Thirty Fund is closely tied to Arabella Advisors, a firm that advises donors and nonprofits about where to give money and was founded by former Clinton administration appointee Eric Kessler. Kessler is president and chair of Sixteen Thirty Fund, and Arabella Advisors provides “business and administrative services” to the nonprofit, according to the tax filing.

Several of the biggest donors and organizations in Democratic politics also have public links to Sixteen Thirty Fund. Potential presidential candidate and megadonor Michael Bloomberg gave $250,000 to a super PAC linked to Sixteen Thirty Fund, Change Now, in 2018. And the Democratic donor group Democracy Alliance, which has dozens of members including billionaire George Soros, recommended last spring that donors invest several million dollars into Sixteen Thirty Fund, according to documents obtained at the time by POLITICO.