Tom Perrielo basically hits on the themes of the upcoming realignment, which is the shift from neoliberalism to populism. He understands that if the Democratic Party emphasizes economic growth and equality but maintains the socially liberal ideology they had they can win a realigning election. There's a reason Hillary won the popular vote with Bernie's platform and it wasn't all Trump's fat mouth.
I think that a lot of it can be attributed to Trump though. I don't think Rubio or Kasich would've lost the PV against Clinton.
They would've, and easily. Trump really WAS the only one who could expose all these flaws. Because with all his, he could foul the whole process up and show the divides as they really are while the media kept trying to artificially even things out for horse-races' sake.
Hillary would've run a 2012-esque campaign and probably won easily given how utterly lacking in charisma everyone else in the clown car was in every sense. Little different from Nixon vs the 1972 field of Democrats in that sense.
Also, Bush '88 pulled it off despite most of the same accusations on him, while Dukakis was an outsider. I have little doubt Rubio would've been Dukakis'd in such a situation.
Trump turned it into 1976 though.
The former case was that of the in-party slowly coming apart and barely holding on, but ripe pickens for booted hard next election with the next big flop and with a moderate caretaker policy in-between
The latter (and the result) is a case of the in-party getting barely taken out by a desperate wilderness party ramming the biggest non-establishment through the convention and hoping it works and thus foisting the struggles onto the new in-party.
Either way, the schism is there.