It's not always easy to find out where candidates get their campaign money.
Even they have difficulty tracking the funds.
For example, Republican Mike Chaney says he spent around $1 million to win the Mississippi insurance commissioner's race in 2007.
Chaney estimates that almost half his money came from the Republican Party. The party reports its contributions, distributing the funds among candidates. It's impossible to say whose donations went to whom.
Another issue is funding for advocacy ads, which played a major role in the insurance commissioner's race. The advertisements don't tell viewers which candidates to support, so the contributions for those ads don't have to be reported.