527 Organisations are named after a section of the US Tax code, 26 U.S.C. § 527. They are political campaign groups officially unaffiliated to individual parties or candidates, and therefore not liable for campaign spending restrictions.
Although candidate committees and Political Action Committees(PAC) are also created under Section 527, the term is generally used to refer to political organizations that are not regulated by the Federal Election Commission or by a state elections commission, and are not subject to the same contribution limits as PACs.
The groups have gained in prominence since 2002, when the McCain-Feingold campaign finance reforms were passed, cracking down on the use of "soft money" in election campaigns.
Critics of 527 groups say they are little more than front organisations allowing official campaigns to run expensive attack adverts without having to adhere to campaign finance restrictions. Examples of 527 groups include the Swift Boat Veterans for Truth.