One of the things I disagree with McCain over is Campaign Finance.  On this subject I agree with Dr. Jerry Pournelle:

Aside on campaign financing: Harold Laski a very long time ago said that wealthy people and companies would defend their interests with money and no laws could be devised that would prevent that. I have seen no evidence that he was incorrect. One can regulate somewhat, but onerous regulations invite the wealthy to hire lawyers to find new ways. My inclination is to fewer regulations and more disclosure. I'd also act to make parties a bit stronger (and able to collect money more easily). I will concede that I am no expert on this but I have spent 50 years being involved in politics and I have some experience in both raising and spending political money. What is very clear is that the present system isn't working very well. As I said, on principle I prefer less regulation and more disclosure.

I don't have Dr. Pournelle's years in politics, but what he says makes better sense than our current system.  Let anyone spend any amount of their personal funds on politics that they wish, but every candidate and political action committee must post the contributions within 24 hours to a public website.