These hypotheses would be impossible to prove out without a rigorous control/test experiment. And even so, because Wikipedia would be just one small component of a politician's or a corporation's communication portfolio, it would be next to impossible to tease out the effect that Wikipedia had, that was not influenced by other factors in the portfolio.
Here's something I find amusing, though...
When Bell Pottinger was discovered to be manipulating clients' entries on Wikipedia, its parent company's stock
(Chime Communications) was trading at about 180. In the following week, the stock dropped to about 165. However, since then, the stock took a dizzying climb up to about 250, before settling out at about 220 now. So, one might conclude that if you do "wrong" by Wikipedia, it's great for your market capitalization!