I wonder if this is true though. Obviously people are lamenting the end of Bernie's campaign now in July, but we've got a lot of time between now in November for Clinton to do some image rehab (potentially with Kaine... we'll see how that goes) and/or for Drumpf to continue to spew horrifying proto-fascist screed. A lot of the Bernie stans I've seen have pointed out the promotion of the platform over the candidate and the legislation, SCOTUS nominations, and other civil liberties that are threatened by not rallying around the Clinton flag. I think there's plenty of time for people to get more comfortable with voting for HRC.
Wonder all you want. If I were in a position to Swiftboat Trump, "A vote for Donald is a vote for Putin" isn't a bad place to start.