here are all the posts I have done on Citizens' United and here are the ones I have done on 527s. Here, though, is a super definition of "super PACs" and a graphic to go along with it. Here is a graphic and definition on 527s. Essentially they two institutions are almost the same. The large difference is that a 527 must be limited to issues and is registered with the IRS as a tax exempt organization and deals with individuals.' Both can accept unlimited contributions. Secondarily 527s cannot talk to a candidate while super pacs have essentially no limitations and can accept any contributions even from corporations. Essentially (and please respond if you think otherwise), super pacs have eliminated the need for 527s.