Sanders is giving people hope, it is the same idea that FDR, LBJ, JFK, and Obama ran on among others. I think that most of the right misses this, practically every left-liberal that got elected in the history of the US ran on this sort of situation in a global crisis. This means that Sanders A) has a shot, and B) the support of the working class. Hope is what got FDR elected to his first two terms.
Second, the economics debate comes down to what theory you support, All left economists, and even a few center-right will say that Sander's plan won't kill the economy, Keynesian will probably say it will boost it, while the right will say that it will be killed by it.
Third, @King Jeffery the republican party actually wants the election to be about those issues, as the US is divided on them about 50-50. If it turns economic or social reform, the Democrats win in a land side(At least 5%). Here's a gallup poll on the matter, read through it before responding, please and thank you.
http://www.gallup.com/poll/188312/2016-state-union-considering-public-opinion.aspx?g_source=&g_medium=&g_campaign=tiles
Edited 2/10/2016 05:26:06