I heard a good analogy a long time ago on Al Franken's radio show. He described people who are still undecided this late in the game like this: "OK, you're on fire, and there's a swimming pool right there. Do you want to jump in?" "I don't know."
The "undecided" voters in Columbus, Ohio (which is where I live, by the way) they interviewed after the first debate, most of them were anything BUT undecided. There was a room full of about 20 of them, and the moderator asked, "How many people were Clinton voters at the beginning?" 4 or 5 hands went up. "How many people were Trump voters?" 4 or 5 hands go up. "And how many people have changed their votes based on what they saw tonight?" Zero hands go up. And whenever the guy went around to talk to the Trump voters, every last one of them rattled off right-wing talking points like they'd been rehearsing them all night. He went to one guy and was like, "Did Hillary do anything to sway your vote to her side tonight?" "No." "Why not?" "Benghazi. E-mails. Blah blah blah."