In American politics, a "527" is a political group, similar to a political action committee
but exempt from limits on contributions to individual campaigns. In return, a 527 is barred from explicitly supporting one candidate over another, or from coordinating with a candidate's campaign.
Some major left-leaning 527's include MoveOn, EMILY's List, Democracy for America, and the New Democrat Network. Right-leaning 527 groups are far fewer: the biggest are Club for Growth and Progress for America.
The name refers to section 527 of the Internal Revenue Code.