Citizens United effectively removed those restrictions.
Who Wouldn't Seek Tax Shelter Under a 501(c )(4) Cover?
Since 2010, the IRS has faced an unexpected flood of applications for 501(c )(4) status from essentially political organizations of all stripes, but especially from conservative organizations. It's hard to find anyone who argues that the IRS responded properly or effectively to this exigency, but it's even harder to find anything but execrable reporting on it either, although there is some good work (by Chris Hayes, Lawrence O'Donnell, Jeffrey Toobin, among others).
Early reporting by AP (Associated Press) May 11 took for story off the rails in the first sentence by claiming that IRS "agents were targeting tea party groups as early as 2011," attributing the claim to a partial draft of a leaked report, and then repeating the claim in the next sentence. The New York Time story the same day started with a misleading reference to "overzealous audits."
The story got so distorted and detached from reality that even the President in his May 13 remarks didn't have much of a handle on it.
Among the accumulating ironies here is that this is the same AP that so agitated the Obama administration that the Justice Department felt justified in carrying out a wholesale trashing of AP's First Amendment rights. But that was apparently because AP got another leak-based story right.
It's Not As Though the Reality of 501(c )(4) Scams Was A Surprise
The first step toward understanding this IRS story is to realize that the problem of 501(c )(4) organizations carrying out political activity that should be illegal is a real problem and is widely recognized.