Then, simplify the tax system. The more complex a system is, the easier it is to game. If necessary, tax revenue instead of profits: if a widget is sold here, the company which sold it should be taxed here.
So, the first thing that should probably be fixed is: no campaign donations, at all.
Campain donations just let the politicians catering to the richer population get more advertising and marketing power.
I'd go as far as forbid all political / campaign advertising. If they want to convince, let them organically convince their local voters, then their state, and up to the whole party etc. Not with costly marketing, videos and large, costly, speaking appearances.