You know Karl Rove's political advertising shop that funnels large sums into campaigns with no disclosure? Apparently, for tax purposes, it's a "social welfare organization":

Crossroads GPS was founded with backing from Karl Rove, a political adviser to President George W. Bush, and concentrated its spending to produce attacks on vulnerable Democrats last year. But the group was formed as a "social welfare" organization under the tax code, allowing it to avoid revealing donor names. ...
Under the tax code, interest groups active in campaigns are allowed to form as nonprofits and keep donor rolls private as long as politics is not their "primary purpose," which typically means that no more than half of their budget is spent on election activity.

Huh. This is a tricky question. Is politics the primary purpose of Crossroads GPS? I guess that depends on whether you consider 100% to be "primary." Not even Karl Rove could argue with a straight face that Crossroads GPS is not primarily a political organization.

Okay, bad example. Rove is a freakishly gifted liar who could, if necessary, argue with a straight face that Crossroads GPS is "a group primarily engaged in promoting dance education for underprivileged youth in the greater Denver area," or that Crossroads GPS is "a small Japanese dinosaur that glows in the dark." But almost nobody else could argue with a straight face that Rove's group is not primarily engaged in politics.

It's kind of amazing that Washington is filled with think-tanks that are bending ovcer backward to avoid anything that hints of partisan advocacy for fear of losing their tax deduction, while Rove is spending money on things like this:

Feel the social welfare!