If my opponent has 30 million dollars, and I have 10 million dollars, I can still put up a pretty decent fight. Citizen contributions will also have less weight, so their inflluence will also be diluted. I agree, and I'm ok with that. Citizen weight should be applied by votes, not dollars. By funding challengers the mandatory sharing proposal will give citizens more choices.
Citizens can save their money for important local causes and charity.
I think both things happen. Judging from the rest of humanity, I think money makes a VERY big difference in how politicians think. I can assure you that money influences what doctors believe. In medical education we go to some lengths to try to limit the influence of pharmaceutical corporations, far beyond any suggested political reform, and they are still too influential. On the other hand, I also think that the current system exerts severe selection pressure.