I think he's could be too far left to win the general. That doesn't mean he can't beat Trump, but he will have the hardest time, IMO. He will be attacked as Socialist/Communist the whole cycle. Yes, they will attack whoever the nominee is with that, but it will stick better with him. He's also too old and hasn't released his taxes which negates two of Trump's biggest issues. I'm also not sure about his foreign policy experience, but that's true of almost everyone.