I really like the Clintons as Republicans. NAFTA, carpetbombing Sarajevo, White House sex scandals, repealing Glass-Steagall... those are prime, principled Republican positions. The anger this election, I think, comes from the fact that we have a Republican campaigning as a Democrat and an autocratic oligarch campaigning as a Republican. If the Berners had any sense they'd throw all their efforts into repealing the Electoral College so that a third party candidate has a hope in hell. I don't really mind the Clintons the way I didn't really mind Bob Dole but I sure wouldn't mind voting for someone who might actually do good instead of voting for someone who will fuck up less.
A dude I've been following on YouTube (so don't take this too seriously, but I don't have much knowledge of USA politics as a Canadian) has been saying the whole Bernie thing is exactly that. To collect a (data)base of progressive Americans, and prepare for the next election, when more people are voting age and boomers are dead. Something something Elizabeth Warren 2020
It's not an uncommon sentiment. The Sanders campaign has some great databases and MoveOn.org started out as a petition to get Congress to drop the Lewinsky scandal. The cynicals among us have zero belief that Bernie Sanders ran for president with the intention of winning the nomination. It would be entirely in character for him to have run with the express purpose of hectoring Clinton into moving left, which she's been forced to do.
That's not even cynical, it's giving him credit for not being completely naive after so long in politics. There's no way he could win, and he surely knew there was no way he could win, and it's much more useful to mobilize an actual left in mainstream politics than to be a socialist President when the current state of American politics places the left at "Reagan", moderate at "the John Birch Society" and right at "herp derp build a wall to keep the brown people out."