Citizens United Explained: How Dark Money Shapes Elections

Citizens United v. Federal Election Commission began as a narrow dispute: the conservative nonprofit Citizens United wanted to air a critical documentary about Hillary Clinton within 30 days of the 2008 primary — which was prohibited under the Bipartisan Campaign Reform Act (BCRA, also called McCain-Feingold). The case escalated into a sweeping constitutional question.

On January 21, 2010, the Supreme Court ruled 5-4 that the government cannot limit independent political expenditures by corporations, associations, or labor unions. Justice Kennedy wrote for the majority that political speech does not lose First Amendment protection simply because its source is a corporation rather than an individual. The Court overturned two prior precedents: Austin v. Michigan Chamber of Commerce (1990) and part of McConnell v. FEC (2003).

What the ruling did not do is equally important. It did not eliminate disclosure requirements. It did not allow direct contributions to candidates (those limits remain). It did not apply to foreign nationals or foreign corporations. The ruling addressed only independent expenditures — spending that is not coordinated with a candidate's campaign.

The practical consequence arrived two months later. In SpeechNow.org v. FEC (March 2010), a DC Circuit court applied Citizens United logic to contribution limits for political committees making only independent expenditures. The result: Super PACs — committees that can accept unlimited contributions from any source and spend unlimited amounts, as long as they do not coordinate with campaigns.

Super PACs (officially "independent expenditure-only committees") must register with the FEC and disclose all donors above $200. Their fundraising is unlimited — a single billionaire can write a $100 million check. Their spending must be independent of campaigns: no direct coordination on strategy, messaging, or ad buys with the candidate. In practice, the line between "independent" and "coordinated" is contested and enforcement is weak.

Dark money groups operate under Section 501(c)(4) of the tax code, which covers "social welfare" nonprofits. These organizations are not primarily political — technically, politics cannot be their primary purpose — but the IRS has defined "primary purpose" as more than 50% of activity, leaving substantial room for political spending without disclosure. Crucially, 501(c)(4)s do not have to disclose their donors to the public or the FEC.

The combination creates an anonymity chain: Donor A gives $10 million to a 501(c)(4). The nonprofit donates $8 million to a Super PAC. The Super PAC reports the donation from the nonprofit — but the original donor is never disclosed. This structure is called a hybrid PAC or "dark money pass-through."

Senate Majority PAC (SMP) — The leading Democratic Senate Super PAC. Affiliated with Senate Minority Leader Chuck Schumer. Spent over $230 million in 2022 and $300M+ in 2024. Primary focus: defending and expanding the Democratic Senate majority. Major donors include George Soros, LinkedIn founder Reid Hoffman, and various labor unions.

Senate Leadership Fund (SLF) — The Republican counterpart, affiliated with Mitch McConnell's operation. Spent $240M+ in 2022. Backed by major corporate donors, Wall Street interests, and the Koch network. SLF and its sister dark money group, One Nation (a 501(c)(4)), form a coordinated fundraising machine.

Koch Network — Americans for Prosperity (AFP) and AFP Action, the political operation of Charles Koch, represent the most sophisticated long-term conservative political infrastructure built on the Citizens United framework. AFP operates in 35+ states, funds policy advocacy, voter registration, and candidate support. The network pledged to spend $70M+ in the 2022 cycle, but notably declined to back Donald Trump's 2024 primary campaign.

AIPAC / United Democracy Project — The pro-Israel lobby's Super PAC became one of the largest single-issue outside spenders in 2022 and 2024, spending over $100 million in Democratic primaries to defeat progressive incumbents it viewed as insufficiently supportive of Israel.

Democratic outside groups also include Majority Forward (a 501(c)(4) affiliated with Senate Majority PAC), House Majority PAC, and various issue-specific organizations. The Sixteen Thirty Fund serves as a major dark money clearinghouse for progressive causes, accepting donations and routing them to multiple downstream organizations.

Research on whether outside spending wins elections is mixed. Money spent in already-saturated media markets yields diminishing returns. But in close Senate races, outside spending clearly influences competitiveness and candidate viability.

2022 Georgia Senate runoff (Warnock vs. Walker) — Total outside spending exceeded $200 million in the runoff alone, on top of record general election spending. Senate Majority PAC and its affiliates spent over $80M supporting Raphael Warnock. The race was decided by 2.8 percentage points.

2022 Pennsylvania Senate (Fetterman vs. Oz) — Over $150M in outside spending flooded the race. Senate Majority PAC invested heavily in Fetterman while Senate Leadership Fund and aligned groups backed Oz. Fetterman won by 4.9 points — within the range where outside spending plausibly made the difference given Oz's self-financing advantages.

2022 Arizona Senate (Kelly vs. Masters) — Senate Leadership Fund initially cut back spending on Blake Masters in October 2022 before partially restoring it — a decision that drew significant criticism within Republican circles. Mark Kelly won by 5 points in a race once projected to be a toss-up.

The clearest effect of outside money is on primary elections, where relatively small dollar amounts can overwhelm a lesser-known challenger or prop up a candidate who cannot self-finance. AIPAC's primary interventions in 2022-2024 demonstrated this: well-funded outside opposition defeated several incumbent progressives in safe Democratic districts.

DISCLOSE Act — The most frequently proposed legislative fix would require all organizations spending on federal elections to disclose donors above a threshold (various versions propose $10,000). The bill passed the House in 2010, 2012, 2021, and 2022. It has never reached 60 votes in the Senate, failing to break a Republican filibuster each time. The argument against it centers on donor privacy and potential harassment of political donors.

Constitutional amendment — Progressive groups have sought a constitutional amendment to overturn Citizens United by clarifying that corporations do not have the same rights as natural persons. Such an amendment requires two-thirds of both chambers and three-quarters of states — an extraordinarily high bar. No amendment has come close.

IRS rulemaking — The Obama administration attempted to define "primary purpose" more strictly for 501(c)(4)s, which would have restricted political spending. After the IRS "targeting controversy" in 2013 — in which the agency scrutinized Tea Party groups applying for nonprofit status — the rulemaking was abandoned under bipartisan political pressure.

FEC enforcement — The Federal Election Commission has a structural problem: it has six commissioners (three from each party) and requires four votes to take enforcement action. Partisan deadlock means many complaints go unresolved. The agency rarely imposes significant penalties on major outside spenders even when technical violations occur.

The fundamental obstacle to reform is that both parties benefit from the current system and both have built sophisticated infrastructure around it. Any reform that constrains one side constrains the other — and incumbents writing campaign finance rules have little incentive to limit the money that helped elect them.