You mean that people vote for a candidate based on fundraising totals?
Please enlighten us on this conspiracy theory.
No, but the majority of voters are not politically engaged or informed and tend to go by what they see on TV. And that means cash to get the message out, to higher people and to maintain "visibility" before the election. A lot of cash. A typical Senate campaign is several million. This isn't being raised from the $10 and $20 from the normal person. It's the people who can marshall many donors to pony up the $2100 or whatever the max is.
The politicians spend a huge chunks of their time fundraising all through their terms (with the 2-year cycle of Congress, it's almost continuous). And the big donor base tends to favor the corporist interests over those of the normal working person.
So if you need at least $5M to run your campaign, and here are groups of persons who can raise several thousands, and over there are people who will give you - much less, let's say, who will the average politician be inclined to please?