Who are these undecideds?

Man, I have no idea. On Twitter it certainly seems like none of the people I follow do. I think it's fairly clear that those who support Trump are either so anti-Clinton that that aspect drives them to vote for Trump, or they feel disenfranchised and are voting for change. Perhaps a xenophobic, non policy based change, but change nonetheless.

But who has yet to make up their mind?

I can definitely see those who have such a poor opinion of both candidates that they are willing to vote for neither. Write in somebody else, vote for Johnson, vote for Stein. The nuclear "Nope" approach certainly exists.

My question is who just doens't know. What reasonable thinking adult, given all that has happen, doesn't know who they will vote for. Interestingly the Luntz focus groups were generally Trump leaning in a debate in which his policy rhetoric and acumen, in the mind of most people I've discussed, went the way of Clinton. But such policy debate, such as that on military strategy on the middle east, will go over the head of the average voter. It is indeed possible that the undecided is a legitimately nice, if not well versed in policy person. They dislike Clinton for any one of a variety of reasons. They dislike Trump, for the obvious reasons. But to them, either their policy understanding is not very well developed, or they simply don't care. Many people don't have a particular interest in politics, but it is interesting question: even among those who don't follow politics, and have scant concrete positions on issues, what leads to an undecided state. What keeps them towards Trump and away from Clinton, vise verse. What will they finally make their decisions upon? Trump audio leaks? A vague impression of having faith in an individual? Oh well, it's not a question I have to answer.