The Supreme Court’s 2010 Citizens United v. FEC decision — a development decades in the making — triggered the flood of dark money by ruling that politically active nonprofits such as 501(c)(4) “social welfare” organizations can spend unlimited amounts to influence elections. Such nonprofits are considered “dark” because they don’t have to disclose their donors, allowing them to bombard Americans with political ads and messages without revealing the identities or motives of the people funding them.

Both parties have come to rely on dark money, but critics say such behavior from Democrats is especially hypocritical. The party has repeatedly introduced legislation to stop anonymous political donations, including a 2019 bill co-sponsored by Harris, and its 2024 platform pledged to “end ‘dark money’ by requiring full disclosure of contributors and ban 501(c)(4) organizations from spending on elections.”