Nah, donors are listed on FEC filings. The only exception would be the “Rusdian nesting doll” situation as posted in the link I provided. Example: a corporation gives 1million , the corporation is listed as the donor, not the board members who donated the $ to the company fund.
In this case we know precisely who donated the funds that constitute this fund.
So candidate X would then likely know his alleged pro-political PAC “fund” quickly dropped by $500,000?
Maybe that too would be secret information. I really don’t know about these insider organizations. Just curious.