Its called the spoiler effect. it is a unfix-able problem of the FPTP system. people cant vote for the person they really want because it takes votes away from the person they are ok with. if they do, they will end up with someone they hate.

Because the people that own both mainstream parties also control the media, and thus control who gets what coverage. If it's not one of their stalking horses then you'll barely hear anything about them and, in a country where the average voter can't tell you how many branches of government there are and what each of them do, out of sight is out of mind.