What is dark money
The answer
Dark money is money spent to influence an election where the public cannot trace it back to the person or company that originally gave it. It isn't illegal. It exists because federal tax law lets certain nonprofits spend on politics without naming their donors, as long as politics isn't officially their main purpose.1 The folk model assumes hidden political money means something illegal happened. The plain mechanic is a tax-code carve-out, not a crime, and that's exactly why it has grown every cycle tracked.
How it actually works
The vehicle is almost always a 501(c)(4) "social welfare" nonprofit, sometimes a 501(c)(6) trade association. A donor gives to the nonprofit. The nonprofit isn't required to disclose who gave it money or how much. It then either runs its own political ads, often framed as "issue ads" that stop short of expressly telling people how to vote, or transfers the money directly to a Super PAC, which can spend it on ads that do expressly support or oppose a candidate. Once the money passes through the 501(c)(4), the Super PAC's public filing shows the nonprofit as the donor, not the individual or company that funded the nonprofit. The donor's name never becomes public record.
The only real constraint is the IRS's "primary purpose" test, a rule of thumb that a 501(c)(4)'s political spending should stay under half its total activity. The IRS has never defined that line clearly, and after the 2013 controversy over IRS scrutiny of Tea Party-affiliated nonprofit applications, the agency pulled back sharply from enforcing it, leaving the rule mostly self-policed.
Brennan Center for Justice found dark money groups put more than $1.9 billion into 2024 federal races, up from about $1 billion in 2020. Of the 2024 total, $1.3 billion moved from nonprofits and shell companies into Super PACs, more than in the two prior cycles combined.2 Brennan Center's own report says this figure likely understates the true total substantially, since dark money increasingly funds undisclosed online ads rather than the FEC-reportable communications the tracking method captures.2 In 2024, dark money tracked by Brennan Center favored Democratic-aligned efforts, about $1.2 billion to $664 million, a reversal from 2020, when Democratic-aligned dark money also outspent Republican-aligned dark money, but by a smaller margin.2 The direction has flipped by cycle. The mechanism has not.
Who holds the power
Whoever controls the 501(c)(4) decides what gets said and where the money goes next. The original donor keeps total anonymity and, often, a tax deduction if the gift first passed through a donor-advised fund, the pattern covered in donor-advised funds as political plumbing.
Where you come in
A Super PAC's donor list is public on FEC.gov. If that list shows a nonprofit rather than a person, the trail stops there, legally, by design. See how to look up who funds your representative for how to pull that list yourself.
Related
Glossary: dark money · 501(c) distinctions · donor-advised fund