If Sanders wins, one thing and one thing only will be responsible - unfettered neo-liberal capitalism. The fact he's been taken anywhere near seriously is testament to the fact that massive numbers of Americans are heavily effected by a right wing ideology that has made them profoundly worse off and a select few disgustingly and unnecessarily rich. You can argue all you like about Marx and Marxism, but time and time again he's been shown to be right on the button when it comes to his analysis of capitalism and how it would evolve - or devolve.
You are right of course, capitalism is a recipe for the masses getting royally screwed whilst the top table gorges on our souls. I do think though that Sanders is the best candidate, he's more of a democratic socialist, if that actually exists. Maybe I'm drawn to him because he's up against people that I abhor, maybe thats the reality but I also find myself agreeing with lots of things he says. I don't for a second think he's an out and out communist, like the opposition would label him as. Maybe I'm becoming more and more left as I get older, but I think the principle I run with, is I like people, I like to think I am thoughtful of others, that making the world a safer more equal place is a good thing.