Sanders, without a doubt.
And I would vote Sanders whether he could win or he could not, because Christie isn't that much worse than Clinton.
Yes, he really is: Christie is way, way worse than most lefties seem able to recognize, and Clinton is likewise not nearly as bad.
I realize this is the case on economics, but I can't vote for any candidate who supports the surveillance state. I often doubt the correctness of my economic views, but I am much more staunch about the surveillance state, which I view as something that cannot be undone if left as is much longer. It might already be too late.