Heads they win, tails they win.
I have long advocated a cure for that problem. All political donations should be ANONYMOUS. A politician can't sell influence if he doesn't know who is buying. To limit the dollar amount of donations would limit the right of constituents to back the candidate of their choice, IOW, limit their FREEDOM. So if an individual or a business believes that the policies of a particular candidate will benefit them, they should be able to fund them as they please. As I said, FREEDOM.
A benefit of this is that politicians will have to make their positions on multiple issues known, in order to encourage donations from like-thinking folks. But since they won't know who gave or didn't give, they won't be able to make moves that specifically favor a business or individual(s).
Finally, make it a felony for the donor to disclose or the recipient to attempt to learn who gave what. Some will try to cheat, but a few frogmarched off in cuffs will give pause to those considering it.
That’s an interesting idea, but I come down more on the side of making it illegal for any entity that cannot legally vote to donate to any politician or candidate. The idea that non-natural persons possess the same God given rights as a human being is detestable on the face of it and makes a mockery of the inalienable rights of actual human beings.