Have you EVER participated in a political campaign, especially at the local level? I've seen well-funded candidates fail because they didn't grasp the views of their electorate.
Once you have a good reputation at persuasion and listening to voters, then funding steps in - not just from corporations, either, but non-profits of all sorts. One of the interesting complaints in China's "human rights report" on the U.S. was that the U.S. government (in compliance with U.S. law) works to uncover large donors to political campaigns. It makes one wonder how many receive covert Chinese funding, yes?