Here's a good op-ed piece on the subject in which it asserts that the squirrelyness of the 501(c)(4) exemption makes problems such all this all but unavoidable. His recommendation?
Let’s get rid of 501(c)(4) status. Encourage nonprofits to forswear political activity and become 501(c)(3)s. If they can’t stomach political chastity, let them become 527s: groups still exempt from taxes but required to disclose their donors.
http://www.washingtonpost.com/opinio...7_story_2.html
Seems like a no-brainer to me.