I keep telling everyone here on the blog and in political conversations to watch the Electoral College. There has not in this election been a point when Hillary Clinton seemed seriously in danger of losing there. Her "lock" states has fluctuated from a low of 218 to a high of about 340 but she's always been ahead by a few points to get her over the necessary 270. (Right now, Nate Silver's three models have here between 291 and 312.) Trump has never been close to a lock on 218.
It might not also hurt to keep one's eye on favorability ratings. As Harry Enten notes, "In every election, the candidate who was leading in net favorability ratings in late September won the Electoral College and the election." Right now, Clinton is more than 10 points ahead of Trump in the favorability rating race…and with Trump ranting about Miss Universe and the new revelations about shady Trump business deals, I have the feeling he's going to lose ground there.
All of this however should be qualified with the reminder that a lot about this election is unprecedented. We never had a Republican nominee brag about his penis size before. And neither candidate is particularly well-liked. Whoever wins is going to be the most unpopular winner ever in that sense…and that's a new thing for America. Usually, we wait until our leaders actually take office before we hate them.