That's where I always* thought this was going!
*OK, there was a 2 week period in Sept when I was entertaining an Obama 2008 margin for Northam, but that opportunity has passed.
Had the financial crisis not hit during September 2015, that race would've been far closer, similar to what the OP poll has for the current race.
2 different factors would've played a role:
1) Mccain was a stronger candidate (than Romney) as he had genuine appeal to PUMAs/moderates.
2) Obama & Hillary basically tied the '08 primary, they weren't that dissimilar from each other in raw electability.