This article published by Campaign Legal Center is by Roger Wieand. Here is an excerpt:

The American people strike a bargain with nonprofit groups: nonprofits get a break on their taxes but must agree to make much of their tax return public.

This transparency is especially important for certain groups that devote huge sums to political spending but organize as “social welfare” nonprofits under section 501(c)(4) of federal tax law in an attempt to keep the sources of that spending secret.

Also known as “dark money” groups, these entities use this secret money to rig the political system in favor of the wealthy special interests that provide it.

Read the full article here.