This is just a guess. Perhaps many of the undecideds are working temp jobs which normally last six months and they are trying to decide the importance of a safety net after the six month contract ends (not that things will really be much different under Romney but they may buy into the ads they hear).
I think most of the undecideds know we’re not in a booming economy.
Then you have the idiots that have no idea.
And perhaps a few hardliner conservatives that still have not decided to vote for Romney but have not decided not to vote for him either.
This is all just a guess on my part. I really cannot relate to an “undecided” voter.