Note that lots of PUMAs -- from polling data, more than this is true of Sanders supporters in this election -- said that they would do that if Obama won the nomination in 2008 rather than Clinton. General election polling data found that that group had evaporated by then.
What people say in anger during the primary campaign and what they do in the fall often aren't the same.
You can't say the same for Sanders supporters. Traditional liberals aren't going to vote Trump under any circumstances.
I think we are in black swan territory.
This is really really dangerous. It's the classic precondition of totalitarianism. Existing politicians in both parties are doing nothing about it. Being occupants of coastal cities (DC) and largely upper class, many don't even seem to realize there's a problem.
Both Trump and Sanders are presenting themselves as such.
I have heard more than one time, if Sanders doesn't win, people claim would switch to vote for Trump. Sounds crazy right, well not so crazy if you partition candidates by "entrenched in political establishment" vs "anti-establishment".
As much as Republicans hate Trump. He is probably their best chance at survival. And this is coming from talking to a "rich old white guy" -- the stereotypical Republican. His comment was that based on current trajectory, Republican party will fizzle away.