No limits. However much money they can manage.
Up to 100 million dollars
up to 50 million dollars
Up to 10 million dollars
Up to 1 million dollars
Up to 500K
Up to 100K
Up to 50K
Up to $200
NONE. All political campaigns should be grassroots with money ONLY from the people
A company could also run an issue ad itself or donate to an industry group that does it, which has the exact same impact - that's the point that you just keep missing. In order for your proposal to work the way you're pretending it would, you'd need to engage in an unprecedented, unconstitutional, and unworkable crackdown on all forms of issue advocacy. It's an awful idea that will never see the light of day and that really highlights that you don't have a firm understanding of how this really works.That's because there are so many holes which you implicitly agree with. Of course other holes would need plugging. You'd have to ban corporations from any kind of political speech (which should be, anyway) and not allow the corporation (union, non-profit, anything other than an individual citizens) to contribute money to 527s and any incarnation thereof.
People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf.