Lessig discussed an idea on this topic in Republic, Lost. If I remember correctly, it was something along these lines:
Donor makes a donation to a politician, which is anonymized. That money is then temporarily escrowed, along with all other recent donations, and the money trickles into the account held by the politician over a certain period of time. That way, donor can't say to the politician "$3mil coming your way, it's from me." On top of that, all donations are refundable so the politician can't trust that the donor actually gave them money and didn't revoke it.
The point of the concept is to limit the information flow between the donor and the politician. The politician can't find out who donated the money, or how much came from a single source, and they can't trust outside information about who their supporters are.
Donor makes a donation to a politician, which is anonymized. That money is then temporarily escrowed, along with all other recent donations, and the money trickles into the account held by the politician over a certain period of time. That way, donor can't say to the politician "$3mil coming your way, it's from me." On top of that, all donations are refundable so the politician can't trust that the donor actually gave them money and didn't revoke it.
The point of the concept is to limit the information flow between the donor and the politician. The politician can't find out who donated the money, or how much came from a single source, and they can't trust outside information about who their supporters are.