I'd hate to be obtuse here but Science, Bitch. People do care whether politicians follow through with their campaign promises, but the politicians don't because what people care about doesn't affect them.

You can speculate that Bush wouldn't have lost his re-election for any number of reasons, it's speculation. And moreso, it's irrelevant because it's pre-Citizens United speculation. The transformation to Oligarchy is a recent development related to more and more pro-corporatist rulings made by the Supreme Court, the latest of them being that money=speech.