McCain-Feingold can't plug all the leaks... Anchorage Daily News article discusses the various types of 501(c) organizations. Tax exempt organizations that are non-partisan generally file under 501(c)3. However, for nonprofits linked to an agenda, the tax code provides a way to get political. And with the Congress sure to increase scrutiny on 527 groups such as Moveon.org in the next session, the nonprofit sector might see an increase in 501(c)4 groups.