And Lessig has been a supporter of Warren's for exactly this reason for years.
Each vote represents a) the path to election but also b) funding for the next election campaign.
In the US, a proportional representation system would have to be enabled by constitutional amendment, I think.
When founding fathers designed the system, they intentionally did not choose to design a democracy because their firm believe was that democracies don't work. This is why they opted for a democratic republic.
One of the reasons why American republic works so well because any small minority can throw a wrench, people can vote with their feet (by moving across states, this is why American federal govt was designed to be so weak, at first it was even weaker but then they had to give it more powers, and today we end up with world's most powerful govt on an absolute scale, but on a relative scale, it can't even shutdown states for a pandemic), and people can vote with their wallets.
Rich people vote with their money directly, but make no mistake, just like disenfranchisement would any minority group will have severe negative consequences, disenfranchisement of the rich and powerful by taking their pretty open medium of participation would also have severe consequences.
American system doesn't just have rich and powerful buying the outcomes, it's just that it's the most open system where anyone can see what they're doing, this makes people comparing it to the rest of the world think that this is a corrupt system, when it is opposite of that.
Believe it or not, it's by design.