OK.
What's the basis for non-taxation in return for political silence, particularly about candidates, and the threat of taxation should an organization endorse a candidate?
And, how can that square with tax-exemption for purely political organizations (527's)?
A link on 501(c)(3) lobbying: http://www.irs.gov/charities/charitable/article/0,,id=120703,00.html
It didn't used to be that way. LBJ was a prime instigator in getting 501(c)(3) orgs out of the electioneering business through changes in IRS regs.
The basic idea is that 501(c)(3)groups who don't pay taxes shouldn't be using that benefit to endorse or work against candidates.
And, how can that square with tax-exemption for purely political organizations (527's)?
Theoretically at least, 527's also cannot engage in electioneering. They can do voter mobilization, issue advocacy, etc. But they still can't expressly say "vote" or "don't vote" for candidates.