Money in the Shadows: Outside Spending Since Citizens United

The bigger picture: the cost of elections since 2000

Start with the whole pie. The total cost of U.S. federal elections — every dollar spent by candidates, parties, and outside groups combined — was about $3.1 billion in 2000. By 2012 it had roughly doubled to $6.3 billion; by 2024 it reached an estimated $15.9 billion. The 2020 cycle alone cost more than the 2000, 2004, and 2008 presidential cycles put together.

Not all of that growth is Citizens United. Campaigns got more competitive, presidential self-funding rose, and online small-dollar fundraising (ActBlue, WinRed) brought in millions of new donors. Some of the increase is simply inflation. But the steepest acceleration — the near tripling between 2016 and 2024 — lines up with the maturation of the super PAC and outside-money machinery the decision set loose. The rest of this report zooms into that machinery.

(The sawtooth pattern is normal: presidential cycles cost far more than the midterms between them.)

Outside spending exploded

In 2012 — the first presidential election after the decision — outside groups reported $1.25 billion in independent expenditures to the FEC. By 2024 that figure had reached $4.4 billion, more than triple the 2012 total and a record for any cycle. Even the midterms tell the story: $788 million in 2014 grew to $2.3 billion in 2022.

Independent expenditures are the most direct measure of outside money: they are the ads and mailers that expressly support or oppose a candidate, paid for by groups acting independently of the campaigns. The FEC totals below are reported figures, not estimates.

Super PACs now dominate

Super PACs — formally "independent-expenditure-only political committees" — did not exist before 2010. By 2016 they accounted for $1.1 billion of the $1.6 billion in total independent expenditures; by 2024 they reported $2.7 billion, roughly six in every ten outside dollars. Add "hybrid" PACs (which keep a separate unlimited account) and the two vehicles created in Citizens United's wake made up nearly $4.1 billion of the $4.4 billion spent in 2024.

The money got darker

Not all of that spending is traceable to a donor. "Dark money" refers to spending by groups — typically 501(c)(4) "social welfare" nonprofits and trade associations — that are not required to disclose who funds them.

OpenSecrets tracked $127 million in such spending in 2010 and roughly $200–300 million in the cycles that followed. The Brennan Center, using a broader method that also captures undisclosed television and digital advertising, estimates dark money reached $1 billion in 2020 and a record $1.9 billion in 2024. By the Brennan Center's accounting, dark money groups have spent at least $4.3 billion on federal elections since Citizens United.

A note on the numbers: the 2010–2016 figures and the 2020–2024 figures come from two different methodologies and are not directly comparable. The early figures count only spending reported to the FEC by non-disclosing groups; the later figures add undisclosed TV and digital advertising. The jump partly reflects better measurement — but every serious estimate points the same direction: up, and steeply.

What this is, and isn't

This is the "high points" view: total outside spending, the rise of super PACs, and the growth of undisclosed money, cycle by cycle. It does not yet break down spending by committee, donor, race, or party — that detail is coming. What the headline numbers already make clear is that the post-Citizens United era moved an enormous and growing share of federal campaign money outside the candidates' own committees, and a large and growing slice of it into the dark.