I know GOP has major demographics problems, but I actually think he could win and it has little to do with him. The Democrats are taking a HUGE risk in essentially giving Hillary the nomination, which her favorability ratings keep falling and where many Democrats are already admitting they've had enough of her. Bernie could also provide a rift within the party, which won't help.
If turnout is low, Cruz has a shot in some of those key states, which makes or breaks the GOP (i.e. FL, OH, etc).
What else can they do? Uncommitted delegates and a Biden movement at the convention? Bernie is just not attractive for those worried about Hillary's electability.
Agreed. THat being said, the "Clinton is more electable than Sanders," an assertion I agree with, is a harder sell to Democratic primary voters than it once may have been, in light of recent polling data.