Being a 501(c)(4) you are exempt from paying federal income tax. Under such rules an organization "is operated primarily for the purpose of bringing about civic betterments and social improvements." So 501(c)(4) are allowed to make political donations as long as it isnt their primary purpose. As of NCAAP v. Alabama 501(c)(4) are not required to disose the name of their donors or the amount they donated. Then you had Citizens United which eliminated all of these rules which limited how organizations may donate. Which left 501(c)(4) in a difficult situation where they can donate as much as they want and not disclose their donations but at the same time cant operate solely as a group to channel money. Obviously this opened a lot of room for false filing. By mid 2010 501(c)s had spent >100m on just midterm elections. The number of filings for tax exempt charities had more then doubled. At this point there was a lot of pressure on the IRS to crack down on political spending by 501(c)(4) groups but the IRS didnt even have the manpower to deal with all of the new filings let alone check to see if they were indeed operating for social welfare and not just tax free PACs. They were begging Congress for 5k new agents, etc.
So obviously to prove a 501(c)(4) isnt just a tax free PAC you need to audit them due to the information you need being protected. So how does an undermanned and swamped IRS know which 501(c)(4) and 501(c)(3) to audit? Well they created a list of keywords to be on the look out for. Words such as "Tea Party", "Patriots", or "9/12 Project", "progressive," "occupy," "Israel," "open source software," "medical marijuana" and "occupied territory advocacy" in the case file would trigger a hold on their application.
At this point it becomes a series of causation v. correlation arguments. 501(c)(4) have always leaned Republican whilst 501(c)(6) have always leaned Democrat. So where more Republican applications caught in limbo because there were just more Republican applications or was it an concrete efford to block conservative 501(c)(3)? Obviously youll find most people in the sub believe the latter.