I'm not sure. It seems pretty likely that Sanders would do well among young voters, even compared to Obama. He might be able to pull in some voters who have sat out recent elections. But (as a Democrat who would be rooting for Sanders in this scenario) I'd be very worried about how well Sanders does among moderates and conservatives (Democrats have gotten 15-20% of the conservative vote in the
last three elections), older minorities and those making more than $50k/year. After years of seeing "socialist" thrown around as an insult, it would be interesting to see how America responds to a self-described socialist.