Koch Group tax exempt status is being questioned. Club for Growth must justify its numbers.

http://www.dailykos.com/story/2014/10/27/1339548/-This-is-Going-to-Hurt-Tax-Exempt-Status-of-Wi-Club-for-Growth-Challenged?detail=email

The pdf file (warning: large file) is available here.
The filing claims that the Wisconsin Club for Growth misled the IRS by claiming $0 on campaign activities in 2011 and 2012 while spending close to $20 million. They spent $9.1 million on the 2011 and 2012 recall elections and funneling $9.624 million to other groups (some controlled by WCfG leaders) that spent those funds on political ads. That spending, the filing concludes, made it clear that WCfG's primary activity "was to elect political candidates in Wisconsin".
The filing goes on to say that the only candidates supported by that spending were Republicans indicating the partisan nature of their spending rather than for the common good of the public.