In 2022, a Chicago electrical equipment manufacturer named Barre Seid transferred the majority of his company to a conservative nonprofit called the Marble Freedom Trust, then donated the proceeds — $1.6 billion — to the organization run by judicial activist Leonard Leo. It was the largest political donation in American history. It was entirely legal. And voters had no legal right to know it existed.
That is dark money. Anonymous political spending channeled through tax-exempt nonprofits, outside the disclosure requirements that apply to candidates, parties, and even super PACs. In 2024, dark money hit $1.9 billion in federal elections — nearly double the record set in 2020. The donors are invisible by design.
How the Mechanism Works
The legal structure is simple. A donor gives money to a 501(c)(4) "social welfare organization." That organization runs political advertising, funds voter outreach, or transfers money to other nonprofits that do the same. No disclosure of donors is required. The IRS allows 501(c)(4) organizations to engage in political activity as long as it's not their "primary purpose."
In practice, the primary purpose rule has never been meaningfully enforced. No 501(c)(4) has lost its tax-exempt status for political activity in recent memory, and the IRS has consistently declined to prosecute organizations spending the majority of their budgets on elections. The rule exists on paper. The enforcement does not.
The money trail can be broken further by routing donations through shell organizations — one dark money group donates to another, which donates to a third. At each transfer, the donor trail resets. By the time the money funds advertising, it has passed through enough legal entities that its origin is genuinely untraceable.
Dark Money in Federal Elections
Anonymous 501(c)(4) spending, 2010–2024
$127M → $1.9B — dark money grew 15x in 14 years. Donors are legally invisible. Voters have no right to know.
Source: Brennan Center for Justice, 2024 Dark Money Report
Who Is Spending
The scale on both sides is significant, but not equal.
On the right, the Marble Freedom Trust — Leonard Leo's network — received the $1.6 billion Seid donation and has spent more than $580 million on judicial strategy since Citizens United: $10 million on advertising supporting Neil Gorsuch's confirmation, another $20 million combined for Brett Kavanaugh and Amy Coney Barrett. The explicit goal was to reshape the federal judiciary through anonymous political spending. Americans for Prosperity, the Koch network's political arm, spent $112 million from its dark money nonprofit in 2022 alone.
On the left, the Arabella Advisors network — a collection of interconnected liberal nonprofits — received $1.3 billion in anonymous donations in 2023. The network funds progressive causes, voter registration drives, and media organizations. It is structured specifically to minimize disclosure. The Washington Post's investigation into Arabella described it as operating "like a Russian nesting doll of dark money."
Both sides play the same game. But the sums are not comparable — and the asymmetry has consequences for which policy areas receive sustained, anonymous pressure.
Dark Money Bought the Supreme Court
The judicial angle deserves direct statement: the current composition of the Supreme Court was shaped in significant part by anonymous political spending.
Leonard Leo spent more than a decade building a network of nonprofits designed to do one thing — move the Supreme Court rightward through strategic judicial appointments. The Federalist Society, the Judicial Crisis Network, and eventually the Marble Freedom Trust functioned as a coordinated system of anonymous spending on Supreme Court confirmations. The donors were invisible. The results were not.
In 2021, the Supreme Court itself struck down California's donor disclosure requirement for nonprofits in Americans for Prosperity Foundation v. Bonta. More than fifty dark money organizations filed amicus briefs in the case supporting the ruling. The anonymous donors who funded those organizations helped eliminate the most direct legal mechanism for requiring them to identify themselves.
The Documentary
The best single resource on how dark money operates in practice is a 2018 PBS documentary that focuses on Montana — one of the first states to see coordinated dark money campaigns at the state legislative level after Citizens United.
Dark Money (2018) — Documentary Trailer (PBS)
The full documentary is available free on PBS.org. It is worth watching.
What Disclosure Would Change
The DISCLOSE Act — which appears in more detail in the reform article — would require any organization spending $10,000 or more on federal elections to disclose donors who gave $10,000 or more. It would not restrict spending. It would not overturn Citizens United. It would simply require that voters know who is trying to influence them.
It has been blocked in the Senate every time it has come to a vote.
The argument against it from Republicans is that donor disclosure enables harassment of political donors. The argument for it from the other side is that voters in a democracy are entitled to know who is funding the advertisements trying to shape their votes. The bill has not passed. The names stay hidden.