The first unknown is turnout. Hillary's supporters are far less enthused about her than they were for Obama. She will receive a larger number of Latino votes, but fewer black votes. What she has going for her is a great ground game, while The Donald is pretty much relying on the Republican party.
The second unknown is the resentment over rising Obamacare premiums. I have spoken to several people who have just received word that their rates are going to double. I doubt very much they will vote for Clinton.