'undecided' = "unsure if I give a fuck enough to go vote for my side"
This seems to have been true for awhile now. The two parties are so different, it's hard to imagine anyone bouncing between the two as if they were close enough to compare.
Which is honestly why I find a lot of the democratic campaigning and rhetoric weird. It seems to still be trying to cater to a group I don't think exists, instead of trying to excite their existing voter base enough into actually voting.