Agree with your points, but it's not about affecting who wins by campaign spending so much as it is controlling the winner after they've won, because then you own them. This is why lobbyists will donate to both sides.
> Compared to economic elites, average voters have a low to nonexistent influence on public policies. “Not only do ordinary citizens not have uniquely substantial power over policy decisions, they have little or no independent influence on policy at all,” the authors conclude. [1]
> much as it is controlling the winner after they've won
But they can only win re-election if (and only if) their constituents believe that they continue to represent their interests.
Also, direct donations to campaigns run by the candidates themselves are ALREADY capped, both for individuals as well as corporations. It is only uncapped for organizations that are not affiliated with the candidate directly (SuperPACs), and this is strictly regulated.
So the point that you're making is: upon winning the 2016 election, if a bunch of billionaires promised Trump that they would donate to an unaffiliated SuperPAC for his 2020 re-election bid if Trump enacted policies opposite to what he campaigned on, he might be able to win his re-election. There is no evidence of this happening. Trump's base will refuse to vote for him if he flip-flopped on his immigration stances.
> Compared to economic elites, average voters have a low to nonexistent influence on public policies. “Not only do ordinary citizens not have uniquely substantial power over policy decisions, they have little or no independent influence on policy at all,” the authors conclude. [1]
[1] https://journalistsresource.org/studies/politics/finance-lob...