This poll suggests Hillary's lead is around 5% nationally.
Actually, no it doesn't. 1). Because trying to guess a national lead from a Montana poll is certifiably INSANE and 2). because even if you wanted to do that, Romney won Montana by 14 when Obama won by 4 nationally, so logic would dictate Clinton is up by 8 now.
Go to math class again.
MT is a small state and McCain won it by 2, while Obama won by 7 nationally, a difference of 9.
Romney won by 14 while Obama won by 4, a difference of 18.
So, it's likely that MT will be anywhere between 9 and 18 points more Republican than the nation.
A 5% Hillary lead looks likely with a 10% lead for Trump there.
Montana is a state with a high ratio of non-college educated whites to college-educated whites. If Trump is lagging Romney in MT he is trailing by high single digits, something like 8-9%