(regarding the earlier discussion of Bernie facing Trump)
I don't think Bernie would have "destroyed" Trump, but I do think he would have won. I figure that he might have had a fairly larger margin of victory than Trump had over Hillary. Trump was reviled, but people (even I) sometimes forget that he did obliterate the GOP field. There was definitely something special about Trump's candidacy. He had the media hanging off of his every word. And besides Trump, Bernie was the "other" exciting candidate that got a lot of people fired up about voting (especially the younger crowd). He was the only candidate that was both exciting AND well-liked.
I've participated in 4 elections (2004-2016), and this was the only one where I was "meh" about voting.
2004: BUSH GOTTA GO! (although I was never excited about Kerry)
2008: ZOMG BLACK PRESIDENT THAT I AGREE WITH!
2012: ZOMG BLACK PRESIDENT THAT I AGREE WITH!
2016: What is this shit?
It's clear that the enthusiasm waned this year (although you could make a case that Trump probably had a lot of enthusiastic voters) and that many crucial voters just stayed home. I take voting seriously and vote in every election (just did early voting yesterday), but it's more than obvious that others are going to need a bigger push. And giving the people an exciting candidate is that incentive they need. I mean, you could chastise people all you want about the importance of voting (Supreme Court! WWIII! Racism!) but at the end of the day, it nets nothing but moral superiority. "It doesn't matter that Clinton wasn't 'exciting'; you still should have voted! Supreme Court! WWIII! Racism!" Meanwhile, Trump is still president, so what have we actually accomplished?
It may very well be a sad state of events that we need a bright, shiny ball in front of us to make us do what we're supposed to do, like voting in every election. People will never automatically care about such things. But if it takes a bright, shiny ball, then so be it. Most voters aren't going to be as heavily invested in politics, and they need that extra incentive to push them over the edge. And I firmly believe that Bernie was that thing (like Obama was to an even greater extent). And if he runs in 2020, then we'll get our answer.
And I could be completely wrong about all of this, but that's just my two cents.