My brother sent along this demographic research firm's discoveries about the undecided voter. He points out one difficulty - that small differences are given equal play in the narrative with larger ones.
I would add that the Undecideds are not a single population, as the wording here would suggest. They are likely two or more separate style of folk who have some overlap. Also, the indecision of voters that is more key to politicians are those who are undecided whether they are going to bother to vote, not who they are going to vote for. The latter exist, but don't offer as much payback. Of that group, the only ones you can get any sort of intellectual handle on are those who are moving from one political or social persuasion to another.