George Will’s list (paraphrased) from some years ago:
1) No limits.
2) No foreign money.
3) Full (and timely) disclosure.
That is, let any legitimate American source contribute whatever they want to whomever they want, but that information is in the public domain to potentially be used against the recipients.
I believed in that too, right up until the California gay marriage initiative (was it Proposition 8?) where the gays got the names of donors supporting traditional marriage through public records, and used the information to harrass them at home and at work.