Alex Lazar reports at Open Secrets:
The 2012 election cycle saw the birth of little-known hybrid PACs, also known as Carey committees, which can maintain two separate accounts; one for contributions to federal candidates and parties, and the other for independent expenditures, to which unlimited contributions can be made. The committees, which emerged as a result of the case Carey v. FEC, collectively raised over $1.55 million in the first six months of 2011, a number that jumped to more than $9.75 million for the same period in 2013 (these numbers do not include ActBlue, which technically identifies as a Carey committee). The funds raised through Carey committees are not getting any smaller and totaled nearly $11.3 million for the first six months of 2015. Approximately two-thirds of this funding came via unrestricted contributions that can only be used for independent expenditures.
Prior to 2010, PACs could only raise funds under existing federal limits – individuals could give no more than $5,000 per year and corporations or unions couldn’t contribute at all. A decision by the U.S. Court of Appeals for the D.C. Circuit in SpeechNow v. FEC changed those rules, allowing new groups that declared they would only make independent expenditures to raise unlimited contributions from virtually any source. This decision is known mostly for creating super PACs, but it also declared that existing federal PACs could create separate organizations to raise unlimited funds to pay for independent expenditures. The District Court Judge in Carey extended this ruling to say that existing groups could simply create different bank accounts (rather than different organizations) to hold these unrestricted donations.