In the upcoming election, I want you to vote for the guy who has no donations from corporations. Hell, I'll even limit it to major corporations. Let me know how many options you have that aren't third-party candidates who are never going to win. Actually if you want a fun challenge, try voting for the guy who isn't supported by the SAME corporations. They usually buy up both sides, just to be safe.
All that advertising candidates do? That is paid for by someone. Mostly corporations. You've been told who to vote for by corporations if you've ever seen a sign supporting a candidate, a commercial, anything. Maybe you didn't listen, but it happened. I grew up in a political family, I've worked in politics for over twenty years, and this is the reality. Ironically when I volunteer in "take back your Government" movements that try and ween people away from corporate candidates, our success rate in convincing people that corporations really have that much control is only 30%. So you're in the majority, most people don't believe it.