That may be part of it this year but this year the rift is very different. Unlike 2008, Hillary Clinton is to the right of Bernie on many issues, even though she tries to sell herself as agreeing with Bernie. Bernie supporters don't believe she really supports the same issues. That wasn't there in 2008. But maybe she can convince them she's close enough to their beloved Bern.
The problem is that it doesn't end there. Sanders supporters aren't just voting ideologically. Hillary Clinton stands for the "rigged system" they oppose. She's cozy with Wall Street. She a status quo insider when they really want an outsider who'll shake things up. She seems phony and untrustworthy, two qualities they prize in Sanders
Of course, there's the elephant in the room, the email scandal. There will be Bernie supporters who won't vote Hillary Clinton just based on the damning IG report. There's also the FBI investigation. It's still going on. Clinton has the indictment cloud hanging over her head too close to the election. Even if the FBI decides that Mrs. Clinton acted properly, people will suspect that President Obama swept it under the rug. We're too close to the election for that story to leave people's minds. I don't know what the Bernie supporters will do. Leaving the Presidential box blank or voting Green/Libertarian or even Republican seem unlikely based on history. Maybe they stay home. They may they vote for Clinton, but it's a mistake to say this election is just like 2008.