Not necessarily that I think McAuliffe is going to romp to victory (hard to see Dems not paying a penalty for a president with middling/low approvals), but Northam's average lead on RCP was +3.3 in 2017. So Democratic candidates posting these kinds of numbers this far out is not exactly unheard of. Source
This is true, but back in 2013, the same polling average had McAuliffe +6.0 and then he only won by +2.5.
Right, but 2017 is closer, so it makes more sense to take the closer result.
Not necessarily. 2013 is the most recent example with a D in the White House.
Overall my guess is that the enthusiasm gap factor will result in Rs getting a boost relative to polling, but that Ds’ new coalition will also give it a boost due to being more reliable. Probably it’ll end up being a wash and therefore final polling averages won’t be significantly under- or over-performed by either candidate.