3. The unhelpful belief that your guy has to WIN in order to get your voice heard is an equally serious problem. It is a mindset that makes people avoid third parties.
Yes, it is true; if you vote for a candidate and he doesn't get into office, it is less likely that your issues are going to be immediately dealt with. It is equally possible that the major-party candidate who is politically closest to your choice may also lose the election.
But here's the thing: the major political parties are aware of this danger too. Third-party candidates can cost them votes, or even an election. That's why they will do anything to shut them out of the process. Currently, the main way they do this is by convincing everyone that voting third-party is "throwing your vote away". But they will also COMPROMISE their policies if it will get them back the voters who would otherwise vote third-party. If enough people start voting for ultra left-wing candidates, you can bet the Democrats are going to swing further left (and vice versa for Republicans) in order to win back the support of their constituents. Voting third-party threatens the status quo; more than anything it sends a message to the old guard about the people's dissatisfaction with their performance.
Voting isn't about getting your guy to win; it is about making your voice heard. Shout loud enough (e.g., get enough people to vote for) for a particular policy and the politicians will listen. It might not happen in the current election but you can bet it will in the next. An election should not be a popularity contest; it is a referendum of the will of the people.
Shake things up; vote third party.