Any citizen should be free to give any amount of his own money to any candidate as long as it is in the open. All contributions should be posted on the internet within 24 hours identifying the contributor --no hidden groups. Transparency is a word used a lot by career politicians who promise it but aren't at all transparent in their actions. Contributors often buy votes that benefit themselves or their business or union --it should all be done in the open so all can know who is giving what to whom.
Candidates in political campaigns should not be capped on the amount of funds they can receive. If someone that supports them decides to make a large donation, then so be it. I see no problem with this at all. All parties are allowed to do it so the playing field is equal.
If funds are unlimited, that continues to allow the elitist system that we have created to strive. As it currently stands, funds are about the only thing that changes from politician to politician. It doesn't matter about ideologies anymore. If one candidate manages to put more of himself out there, the uneducated masses will believe he is the better choice.
If there are two candidates for office, and one has unlimited access to funds that the other candidate does not have, the rich one has an unfair advantage. They can put themselves in the media more often and win more votes just because the other candidate hasn't enough money to be seen by the voters. Being seen means more to people these days. Out of site out of mind.
Countries with more fair and open elections, with multiple parties and more choice, are countries that set limits on advertising and political campaigns. Money itself does not equal speech, especially not corporate money. The best way to move forward is to support public financing of campaigns so that people focus on real issues and debates rather than getting manipulated by micro-targeted voter conversion models and media buys.