If Bernie wins the primaries, the upperclass republicans will shift back to the right because he's coming after their money. Traditional big money needs a political home and Bernie's wing is making the democratic party uncomfortable for them. Also making them irrelevant in campaign financing. If that doesn't work then the new left and the new right will both be in the democrat party. with the republicans serving as a backbone from the new-new left while also disintegrating into 100s of goofy little parties that reflect their online factions.