There is no hard cap and no limit on doing things that don't cost money so no one is ever prevented from speaking (that would open censorship challenges). It doesn't need to survive strict scrutiny because all candidates are treated equally making it viewpoint neutral topic discrimination. And Congress has a long established power to tax basically anything they want.
Or it creates an entirely new problem. People like this don't just go away after hitting a single roadblock.
Federal regulation would make a mess of the idea due to preemption, eliminating the state regulatory option and leaving us with just the federal options of a Constitutional amendment or impeaching/replacing the Supreme Court and repudiating their openly corrupt precedent (decree).
If we just change the rules, the game will stay exactly the same? Sorry, but this awfully naive.
The current court is completely partisan and has zero judicial theory other than backing partisan power and oligarch power. They have the final say on how to interpret the constitution but reject the founding principles of the USA.
That said - yes, they need anti corruption / bribery regulation, fixed terms, and those terms to be co-prime wrt political fixed terms.
* https://www.abc.net.au/science/archive/articles/2001/11/27/4...
There's a free speech issue to saying "you can't advertise your own opinions". Where is the line? Should every charity that "raises awareness" be banned? Should every sponsored Youtuber be forced out of political commentary? (I mean, I don't hate the idea completely ....)
There's the skeezy links behind organisations that support a political stance, and claim no real links to politicians. But we know that it's all kinda bs with strong links between the "nonaffiliated" "Political Action Committees" that claim to just represent causes and ideas, and the politicians who just happen to be close friends with the organisers. But it's rarely totally black and white.
There's a free speech issue to letting money make someone's speech be heard louder than others, making most other people's speech technically free, but inaudible.
Most countries have limitations on the broadcasting of political opinions and candidate support for periods before elections.
These laws don't work as well these days with the importance of social media (and it's mostly the same rich Americans that take advantage of this to meddle into European affairs) but at least the principle is there, while I think the fundamentalist way that the US interpret "free speech" prevents anything from being doable at all to curb the undue influence in politics that money can give.
Indeed, as the UK is finding out at the moment, the existing rules are insufficient and it's turning out that a rule is only a rule if it is enforced anyway.
Allow civil suits when promises made aren't kept.