The Slouch- This person simply lacks interest and has not taken the time to be informed. What he does know is based on what the candidate looks like, campaign ads, friends and so on. This person can be characterized by his discomfort or dislike of discussing politics for fear of his ignorance being revealed. I would say that this constitutes almost all "independents" and explains why the same state can elect a president that wants to go in one direction and a senator that wants to go the opposite direction. Oh yes, they then complain about the "partisan divide".
The Utopian - This person views the world through a lens of perfection. While being sufficiently informed about what the two candidates stand for, this person rejects both because neither comes close enough to his idea of perfection. This person's understanding of politics reflects the vision he hopes to achieve through an election in that both his vision and his candidate can be defined as narrow. His candidate will never win a primary because the candidate must appeal to a group with little to no tolerance for those who see the world differently. The election process for them, after their guy looses the primary, is to trash the winner in order to create a platform to vent their frustration about reality. Their numbers include people from both the right and left. I would say however that most are from the right because, in my opinion, the right contains greater numbers of informed and principled people. I base this opinion on the fact that the left extracts most of its appeal and power by the promise of redistributed (read free) wealth; which means all anyone really need be informed about is who is promising more free stuff. This is a question easily answered by party affiliation.
The Principled - This person rejects both candidates on principle. He sees himself as not being able to cast a vote for any person who does not meet a minimum level of morality... come what may. This type understands the ramifications of not voting. He understands that there will always be a "better" candidate that will serve any given person better than the other, and therefore will be a better candidate for his own sake. But he shuns the perceived advantage and rejects both anyway. This person differs from the "Utopian" in that he understands the political realities within which he exists. He has a high tolerance for differing opinions because he realizes that his vision is meaningless unless it can be converted to meaningful reform by winning elections. That tolerance has its limits however, and the limits are exceeded when neither candidate can stand or appeal to the same or similar principles.