I've been saying since day one he won't win in the general election, for two main reasons.
1. How motivated will the Bernie Sanders wing of the party be to turn out and vote for him? Sure they hate Trump with the passion of a thousand burning suns, but actually coming out to vote for someone who's just about everything they claim to be standing against (white male billionaire) takes some serious nose-holding. (especially if they feel their guy got screwed out of the nomination again)
2. His extreme anti-2A positions have got to be alienating to those more moderate voters who care even a little bit about their gun rights.