his politics are far outside the mainstream.

Sanders disputes that. What do you make of these polls --- reviewed by WaPo: Americans largely support his positions?

due to over-representation of rural states.

The alternative view is that Democrats lost rural states when they abandoned core economic issues --- first getting lost in the morass of identity politics (in the 70s). And after the fall of the Eastern block, the left lost confidence in criticizing Capitalism, and we got a stream of underwhelming, unconfident Democrats like Mondale and Dukakis (who ran away when called a liberal), and then third way Democrats took up positions on the right of the Republican party.

What rural and information-poor voters then saw was a Democratic party without a unifying message - rather one with slick politicians selling positions to different interests groups - the Democrat's big tent.

FDR won majorities in conservative states by hitting economic issues head on, and explaining to people how they were being cheated. Right now, people feel that --- and this is the root of the anti-establishment feeling.

The fact of the matter is Sanders is an almost guaranteed failure in the general election.

Not convinced. Why is he the only politician with net positive favorability? What happens when people realize that his policies are what they want?

I think the standard analysis discounts the huge numbers of voters who've dropped out of the process from frustration and disgust. It also ignores the politics of the 30s-70s when Democrats took populist economic positions and won huge majorities in what are now considered solid Conservative states. For example, how do you account for the fact that a Socialist held the biggest gathering of any candidate (12,500 people) in a Red state?