he doesn't have a ground organization
This is what will do him in. Nothing else, just this.
The debates, while a grand exercise in seeing how much we can debase ourselves in front of a worldwide audience, don't accomplish anything in this cycle; there is no sizable chunk of undecideds to sway, and they aren't talking about policy anyway.
What undecideds there
are out there, are exactly the kind of weak willed jellyfish that a good ground game gets you (along with motivating the people who were going to vote for you anyway, and just need an extra oomph to get to the polls).