The current voting system leads to an inevitable bipartisan system in which the most people are not represented by their ideal candidate and instead vote out of fear of their least favorite candidate.
CGP Grey has a very informative set of videos explaining it http://www.youtube.com/playlist?list=PLNCHVwtpeBY4mybPkHEnRxSOb7FQ2vF9c.
This is particularly relevant in this election as a great many people feel that neither candidate is fit for office, and that a candidate we can all confidently vote for would improve the unity and progress of this country.