So this probably doesn't have much impact at all.
One appealing idea I heard is that every American gets a voucher they can allocate as they see fit, from a pool of tax money allocated to the elections. Candidate should probably get a fixed pool as well
Citizens United ruling is what opened the door to PACs and the ability for individuals to spend above the individual limits
I haven't looked at the research myself, but among Economists this is an established fact.
To me, this is good news. The cynical view that anyone can buy an election by outspending their opponent is depressing, and I'm glad it isn't true.
BTW, it is true that the candidate who spends more usually wins. But that mostly just reflects that they're the most most popular candidate, so they get the most donations.