That is just trying to regulate an addicts intake of drug. Private campaign funding, period, is a corrupting influence in any form.
The real solution is public campaign finance. We have this lovely new thing that enables instant communication between anyone, anywhere called the Internet, where information duplication and propagation is effectively free.
Start there. Anyone can be a candidate on a state run open source collaborative hosting service for political campaigns. Those represent the first layer - to not alienate the technologically disinterested, provide TV time and dead tree info pamphlets on the top candidates. The difference is that right now you take bribes to enable you to saturate peoples attention on TV and in print, with this system the state buys the face time and the viable candidates share it.
No, it is not perfect. You have the problem of view distortion where anyone who is abjectly against technology won't have their voice heard early on in the process. But Facebook has really demonstrated the ability to motivate people to engage with technology where they would never have fathomed doing it before - I strongly feel a properly implemented system like this would get extremely high adoption and engagement rates, well beyond what we get now with traditionally ad driven campaigns run by laundered money.
The good news is if you do cut money out of campaigning cold turkey then it is very easy to see the vectors of corruption - paid for political speech is an obvious violation, so you don't get private "third party" campaign ads. Part of running for an elected position can be the requirement of full financial disclosure - we know who pays you, and for what. Any time money changes hands for political ends you can directly prosecute on those grounds alone - because you aren't allowed to privately finance your political interests, you have to use public forums.
There is a lot of nuance in such a system, and much nitpicking. But the fundamentals - anyone can run, and the viable runners get public airtime shared by viable candidates equally - and where paid promotion is astutely illegal - you can dramatically cut down on campaign corruption in ways just trying to limit contributions (again, it has been an ongoing and losing battle to control private finance of political campaigns since the country was founded) cannot do, because innate in the idea of private citizens giving money to candidates to then spend attracting more citizens to support them you have a feedback loop that enables corruption because any citizen can be bought off on who they support and they can just be an indirection of big donor monied interests cash going into the pockets of crooked politicians.