They'd rather lose with Hillary than win with Bernie.
Tell you what jfern...prove that Bernie is guaranteed to win and that Hillary is guaranteed to lose and I'll switch to supporting him.
Of course there are no guarantees, but all the evidence has Bernie doing much better.
What evidence? There is no evidence. Pointing to a poll is not evidence, especially when Bernie has not gone through media vetting or the GOP attacks that will surely come his way. How does Bernie defend himself against an ad that says "Bernie Sanders, a socialist, want to take away your private health insurance and raise taxes on all Americans," juxtaposed with videos of Bernie says these very things.
Fact is we don't know how Hillary Clinton or Bernie Sanders will hold up in the general. We can't predict the future. If polls were indicative of who will be President then in 2012 Romney should of been elected, in 2008 McCain should of been elected, in 2004, Dean should of been elected, in 2000 Gore should of been elected, in 1992, Perot should of been elected, in 1988 Hart should of been elected etc etc etc.