Actually, not a few Sanders supporters initially were planning on saying fuckit and going for Trump, many of us have been talking them off the ledge and pointing at Jill Stein. Who, BTW, is the only progressive choice on the ballot. Remember when the DNC jiggery-pokery started becoming pretty evident? Jill Stein offered to relinquish her spot on the top of the Green ticket and was all in favor of Bernie taking her place since the Green convention took place after the DNC convention. She and Bernie are extremely close in views and platform and she is the ONLY candidate who has even had a word to say about climate change and clean energy.
As for spelling it out--trust me, it's being done. Not on mainstream media, who are very carefully leaving out the Green party and Jill Stein on polls and news, but the word is out there. As for "remembering 2000" it's been disproven over and over and over and over and over and OVER that Nader had any effect on the outcome whatsoever. Gore didn't even carry his own home state, FFS, and there were a lot of other factors that made that shit happen--Nader just got the blame but it's all bullshit.
Because of the electoral college, your third party vote has absolutely no effect whatsoever on the eventual outcome, unless you live in VT and plan on writing Bernie in. Other than that, your third party vote CAN count in a very real and tangible way, by securing federal matching funds for the Green (or Libertarian, if you simply MUST
) party in the next election. If you really want to make a difference, vote using ONLY an absentee paper ballot (avoiding voting machines is critical if you want your vote to have a snowball's chance in a cyclotron of being counted accurately) and vote third party. You can't hurt a damned thing but you could help set up a win next time around.