This whole notion that 501(c)4 groups are receiving some kind of huge implicit tax subsidy whose use needs to be policed is simply absurd. I am a board member of several 501(c)6 trade associations, which have roughly the same taxation rules as 501(c)4.
The largest tax subsidy, by far, available to some non-profits is the deductibility of donations to the group. This is available to 501(c)3 groups (traditional charitable organizations) but NOT to 501(c)4 or 501(c)6 groups. Whether the Tea Party of Cincinnati is a 501(c)4 or not, you cannot deduct your donations to them.
The one tax break that 501(c)4 corporations get is that they do not pay taxes on any surplus they accumulate in a year. In general, non profit groups like this collect donations and spend them. So in general, their outlays match their revenues, such that they tend to show very little income anyway, even if it were taxable. The only thing the non-profit status brings to 501(c)4 organizations is that they don't have to spend a lot of time and effort trying to make sure, at the end of the fiscal year, that expenditures and revenues exactly match. Basically, the one benefit granted is that these groups can collect money in November for expenditure in January without paying taxes on this money. This is hardly much of a subsidy, just a common sense provision. (By the way, at least in a 501(c)6, there is no break from the paperwork. We will have to pay an accountant to file a tax return for the Feds and the state of California.
This actually comes up from time to time in my industry. A couple of my competitors are actually non-profits. My for profit competitors always complain that these non-profits have an advantage, arguing that they are really for-profit, but just paying their "owners" large salaries rather than dividends. My general answer is, so what? My company is a subchapter S corporation, and it does not pay taxes either -- I pay taxes on the profits as regular income in my personal tax return, exactly as if I had paid out all the profits as salary. Sure, it would be nice to accumulate profits in the company tax free, but seeing the shoe-string way my non-profits competitors run, I don't think that is what they are doing. It used to be that as non-profits, they considered themselves immune to certain laws, like the Fair Labor Standards Act and minimum wage, but the courts have disabused them of that notion. So it is hard to see what advantage they enjoy, but folks love to complain none-the-less.
The only real business advantage I have ever found these non-profits have is in perception among leftish politicians -- they are considered "clean" while as a for-profit company I am considered "dirty". Which is why in California, early laws allowing outside companies to operate public parks allowed non-profits but not for-profits, and almost every state who goes this route tries non-profits first for the same reason. This no longer bothers me -- anyone who had ever been part of a non-profit can probably guess the reason. They really are not set up to operate a 24/7/265 service business, and within a year typically fall short, and I, with a bit of patience, then get my chance.