Are all political contributions corrupt? If so, would we be better off banning them altogether? (Of course, then the only people who could afford to run success

Are all political contributions corrupt? If so, would we be better off banning them altogether? (Of course, then the only people who could afford to run successful campaigns would be the independently wealthy...) If not, where’s the line? Citizens United was a case about a relatively narrow question, and the opinion was well reasoned. I believe it was correct. If you think it was wrongly decided, where’s the flaw in its logic?