Nader/Gore might be increasingly irrelevant as the years go by but it's not yet irrelevant. It was only 16 years ago. The people who didn't live through it haven't even voted yet. They say everyone remembers where they were when Kennedy was killed. I was born in 57 and I knew and was affected by the Kennedy assassination even though I was too young to remember where I was when it happened. Memory extends backward a bit more than we're aware of. We're affected  by the discussions of events in the near past that we didn't or barely lived through. 

The democratic primary was a relatively brutal affair and Sanders refusal to accept his loss spread discontent to his supporters. But still according to the statisticians the vast majority of Sanders supporters voted for Hillary not Jill Stein.

Kids supporting their parents despite who they are is common. I don't accept that as a convincing argument for your theory. Jared and Ivanka may have followed their father to the republican side but those who liked Ivanka and bought her clothes, books and other products didn't go with them. They dumped her and her products immediately and didn't even give her a break due to familia loyalty.

Sanders polled as poor name recognition early on. Of course he could beat Iowa to death over a year, and New Hampshire next door would recognize him, but the rest of the country was a tough sell (and like with Obama, that relative new-to-the-scene was a plus in a country where media uses familiarity as a riding crop).

Check out early electability before the media full court press started - she was in fine shape.

Hillary would have done better if able to run as the non-favorite. Being #1 meant both in 2008 & 2016 the media would try to second guess and create a horse race out of it. How many times did we hear Joe Biden blah blah blah, Michael Bloomberg blah blah blah, some other savior of a candidate was going to come in and spice things up (some ridiculous character I can't remember right now.... They couldn't be bothered to actually analyze any policy presentations - instead they just acted bored and looked around for an alternative to pay their bar bills. It was much like 2000 except George Bush was moderately warm and likeable in a fratboy kind of way when not a snippy asshole, while Trump was an obnoxious dirtbag, but still he knew how to suck up all the oxygen out of the room while all the other GOP candidates were seriously boring along with occasionally full bullgoose loony.

And yes, she could abandon Obama but then she'd be the ungrateful traitor and lose the black vote among other, or lash her line to his sails and ride out the iffy establishment/go-it-slow reputation. While Bernie didn't have to run on any record or much defend any past behavior. He could have a kid out of wedlock and that makes him cool. She could keep quiet about women who slept or said they slept with her husband 20 years before, and that just made her a conniving bitch who tried to destroy them - thus Trump parading around Bill's mistresses at the debates. Really amazing to consider this fuckwad pulled such a trailer trash move among so many and still got elected President. Independents? fuck people - how many independent morons deos it take to elect a trainwreck of a President? who knew we had such a surplus of congenital idiots, many of whom still maintain that somehow HIllary would have been worse, based on what, I still can't grok.

And no, we can't discount billions spent building up Fox & Breitbart over 20 years along with whatever Mercer & Koch Brothers spending known and unknown - Hillary spending a half billion over a year doesn't make up for year after year after year of irrepressible propaganda. Consider that the right basically recovered its position about 3-4 months after Bush crashed the economy, while BIll Clinton took more blame for 9/11 under W's watch than W did. Very effective propaganda. Guess they're all cowboys, independents out there following those pipers in their head, but when we talk about a parliamentarian system, we have to differentiate European ones where candidates and supporters are still largely sane, while the US political system has jumped the shark. Happy Days it ain't.

I can't figure out what the "next" is. Bannon-esque fascism? Sanders-ish democratic socialism? None of it seems likely.

That's kind of the point, isn't it? Nothing seems likely but anything is possible. The Overton window is now as wide as a barn door, people are expressing opinions that seemed wildly politically implausible last year and pushing policies no one would have thought worth considering. Trump is horribly unpopular, but I have yet to see the Democrats looking inclined to promote anyone any less unpopular. There is no reason to expect a recession before the mid-terms so given gerrymandered districting I wouldn't expect any change in the short term. 

Contra what you say in your first paragraph, I think the only thing that is predictable is that there will be surprises: First of all it's still not unlikely Trump will get reelected. Gallup puts his approvals at 39% now after Charlottesville. Back at election time 2016 his favorables were 39.5%. If he doesn't upset his base any further, he will have a decent chance. Depending on how badly the Democrats screw up who they nominate next time around. Not sure his reelection would count as a surprise, but everyone seems to be assuming it won't happen.

Also, the idea that people are looking to a sedate centrist to bring everyone together sounds wildly wrong to me. There is no center, in the sense of economically conservative but socially liberal. The idea tha that anyone wants more free-trade agreements, more corporate subsidies, concentrated markets, and entitlement cuts is nuts. 

The left is slowly getting organized and will challenge the Democratic party establishment making the primaries more interesting than before. The nationalist right is looking energized and the corporate establishment has lost its credibility. Candidates can come out of nowhere, with little preparation of the terrain. Trump set up his small-donor network in no time. No need to schmooze the establishment elders for four years. No one cares what they think anymore. Endorsements are worthless.