Not to diminish your understanding of your friends, but I predict when it's all said and done and Hillary is the nominee, they will. Lock-step voting is part of the liberal conditioning and has been for decades.
In my experience, even if they won’t vote for her in the Primaries, they will march in lockstep and vote for her against a Republican.
There is maybe 3-5 % of the vote that is up for grabs. A candidate like Fred Thompson, should he decide to run, or Rudy, might appeal to those people.