The general rule is that a charity must operate “exclusively” for charitable purposes, but the Regulations make clear that “exclusively” only means “primarily.”  Therefore, if the charity provides free services to a (c)(4) social welfare organization, even if it is deemed to be for noncharitable social welfare services, the total activity may not be sufficient to jeopardize the exemption.  Better than giving the services, however, would be to charge the (c)(4) for the services and make a little money for the charity from the mark-up on the portion of the fundraiser’s time spent working for the (c)(4).  Even if the income were to be considered unrelated business taxable income (and it is not entirely clear that services to an associated organization would be unrelated to the purpose of the charity), it is not likely to be a problem.  It is not a good idea for a charity to give anything to a (c)(4) but there are always arguments that it is not “too much.”

I would not take the same view with the fundraiser providing services to a political action committee.  The prohibition on participating on a political campaign is absolute, and a charity can lose its exemption if it engages in any political activity for any election at any level of government.  (See Ready Reference Page: “IRS Has Not Changed Guidance on Electioneering”). Charities do not violate the prohibition by holding debates where all viable candidates are included or where they rent their auditorium to a candidate on the same terms and conditions on which they rent to others of the general public.  But there is no way you could offer your fundraiser’ services to all political candidates.  The fundraiser’s services on behalf of a single PAC would undoubtedly be attributed to the charity. 

Although the Internal Revenue Service does not frequently enforce the prohibition these days, I would not put myself in a position where the IRS might be able to challenge me.  Better to have the fundraiser work separately as a part-time employee of the PAC and a part-time employee of the charity, with very careful allocation and records of the time for each.  It would be a little bit more administratively complicated, but it wouldn’t risk the very existence of the charity.