The biggest problem with the campaign-finance system is also the hardest to correct: the escalating millions spent on politics behind a veil of secrecy. On its face, this should be an easy problem to fix. Why not simply require donor disclosure for all campaign activities?
The hard part is that many groups that claim to be engaging in advocacy or public education are actually making political expenditures. The courts have ruled that advocacy groups have a right to keep their donors private, lest the government tread on constitutionally protected free speech.