If they Bushes come out for Clinton, or against Trump, one step further in the next 6 weeks - I guarantee they are signing their own political death warrant.
They will NEVER escape the “traitor” label.
(Now, if George W endorsed Hillary, it might swing a few luke-warm repubbies (conservative admirers of Bush) away from voting for Trump, but George W. Bush is so hated by so many democrats (and the socialists/Bernie-supporters and voters and donors and workers and enviro's outside of Washington and the ABCNNBCBS press corpse) that the final result is a LOSS of potential Hillary voters in the general election.