The phrase outside money appears constantly in coverage of American elections, but the organizations behind that money are not all the same. Traditional political action committees, super PACs, and independent expenditures are distinct legal categories, each governed by different rules about how much money can be raised, how it can be spent, and how closely the groups may work with the candidates they support. Sorting out these categories is essential to understanding modern campaign finance, because the differences between them determine both the scale of the spending and the legal lines that the spenders must not cross.
A traditional political action committee is the oldest of these vehicles. It raises money from individuals within legal limits and uses that money in part to make direct contributions to candidates. Those contributions are capped, commonly at 5,000 dollars per candidate per election for a multicandidate committee. In return for accepting these limits, a traditional PAC is permitted to give money straight to a candidate's campaign and to work openly with that campaign. The defining trade is simple. The committee accepts limits on the size of its gifts, and in exchange it may contribute directly and coordinate freely.
This trade between limits and access reflects a basic principle that the Supreme Court established in its 1976 decision in Buckley v. Valeo. In that case the Court drew a distinction between contributions and expenditures. It held that the government has a strong interest in limiting direct contributions to candidates, because large gifts can create the appearance or reality of corruption. At the same time, the Court treated independent spending differently, reasoning that money spent independently of a campaign poses less risk of a corrupt exchange and therefore deserves greater protection. This distinction between giving to a candidate and spending on one's own became the foundation for everything that followed.
An independent expenditure is money spent to support or oppose a clearly identified candidate without coordinating that spending with the candidate or the candidate's campaign. A group that buys an advertisement urging voters to support one candidate or to reject another is making an independent expenditure, provided the spending is genuinely independent. The key word is independent. The spender must act on its own, without consulting the campaign about the content, timing, placement, or strategy of the message.
Because the Supreme Court in Buckley treated independent spending as deserving strong First Amendment protection, independent expenditures have never been subject to the same dollar limits that apply to direct contributions. A person or group could always spend unlimited amounts on truly independent communications. What changed after 2010 was not the freedom to make independent expenditures, but the freedom to raise unlimited money in order to fund them.
The super PAC emerged in 2010 as the product of two legal developments in the same year. The first was the Supreme Court's decision in Citizens United v. FEC, which held that the government could not prohibit corporations and unions from spending their own funds on independent political communications. The second was a decision by the United States Court of Appeals for the District of Columbia Circuit in a case called SpeechNow.org v. FEC. Reasoning from the logic of Citizens United and Buckley, the appeals court held that if independent expenditures cannot corrupt a candidate, then the government cannot limit contributions to a group that does nothing but make independent expenditures.
Together these decisions created a new kind of committee. A super PAC, formally known as an independent expenditure only committee, may raise unlimited sums from individuals, corporations, unions, and other groups, and may spend unlimited sums on independent expenditures. In exchange for this freedom, a super PAC accepts one crucial restriction. It may not contribute money directly to candidates or their campaigns, and it may not coordinate its spending with them. The super PAC trades direct access for unlimited scale, which is the mirror image of the trade made by a traditional PAC.
The single most important legal boundary governing super PACs and other independent spenders is the prohibition on coordination. Independent spending is constitutionally protected precisely because it is independent. If a super PAC were to coordinate its spending with a candidate, the spending would function like a direct contribution, and the entire justification for allowing unlimited fundraising would collapse. For that reason, federal regulations define coordination in detail and forbid it.
In practice, the line between independent and coordinated activity can be difficult to police. Candidates and the super PACs that support them are often run by people who know one another, and campaigns frequently post information publicly in ways that outside groups can observe. Enforcement of the coordination rules has been a recurring subject of debate, with critics arguing that the line is blurry and supporters of the system arguing that genuine coordination remains prohibited and punishable. Whatever one's view, the no coordination rule is the legal hinge on which the whole structure turns.
Between the traditional PAC and the super PAC sits a hybrid form sometimes called a Carey committee, named after a court settlement that recognized it. A hybrid PAC maintains two separate bank accounts. One account follows traditional PAC rules, accepting limited contributions and making direct gifts to candidates. The other account follows super PAC rules, accepting unlimited contributions and funding only independent expenditures. By keeping the two accounts strictly separate, a hybrid committee can participate in both worlds at once, giving limited money directly to candidates while also spending unlimited money independently.
All of these committees operate within the federal disclosure system, although the details of what they reveal differ. Traditional PACs and super PACs alike must register with the Federal Election Commission and file regular reports listing their receipts and disbursements. Super PACs must disclose their donors, which means that the individuals and organizations giving to them generally appear in the public record. Independent expenditures themselves must also be reported, and large expenditures made close to an election must be reported quickly. This reporting is what allows the public to see not only how much outside groups are spending, but in many cases who is funding them.
There is an important limitation to this transparency. A super PAC may accept money from organizations that are not themselves required to disclose their donors, such as certain nonprofit groups. When that happens, the super PAC's report will show the nonprofit as the source, while the original individuals behind the money remain hidden. This layering is one of the main ways that the source of some political spending becomes difficult to trace, a subject that belongs to the broader discussion of disclosure and dark money.
The differences among these vehicles are not merely technical. They determine how much money can move, who can give it, and how directly it connects to a candidate. A traditional PAC offers limited but direct support that the candidate controls. A super PAC offers unlimited but independent support that the candidate may not direct. Independent expenditures can come from many sources and can reach enormous totals in competitive races. For anyone tracking the flow of money in an election, recognizing which kind of group is spending, and under which set of rules, is the difference between reading the numbers and truly understanding them.
See it in the data: Track direct contributions and outside spending in 2026's competitive races with our Campaign Finance Tracker, pulled live from the FEC.