The 2 major parties are both seeing signs of fracture. The republicans are probably closer to a split than the democrats but it wouldn’t be surprising to me if you saw a 3 or possible 4 party system in the not so distant future. The socially conservative base of the republican party is certainly unraveling as the glue to hold the party together. The parties for decades have been holding themselves together via moral/social issues but those issues are becoming less important to Americans’. How long ago was it that your stance on abortion was the biggest factor in the election? Now that’s probably not even in the top 10. Fiscal issues are becoming a much more important. Both Trump and Sanders popularity is one of a fiscal nature, not because of their stance on abortion, LGBTA rights, or some other social issue. It’s that shift in priorities which is baffling the political pundits.
The other big factor is the disregard for the rule of law in this country. There’s far too many people above the law and people are upset with it. There’s frauds everywhere and people want somebody to hold them accountable. Nobody ever goes to jail. Clinton isn’t going to have anybody locked up. Sanders or Trump might.