Why can’t Dems get over the hump in NC?

[Skill and Chance]

1. Dems lost rural support more slowly in NC than pretty much anywhere in the South.  Not losing rural white voters by as much of a landslide as other Southern states was a very underrated factor in the 2008 win they can't seem to replicate.  Now, the losses are extending to rural minority voters.

2. Retirees moving into the coastal areas are creating something of a Florida effect

3. The inland western part of the state (but still east of the mountains themselves) just keeps getting more R.  It has some Rust Belt characteristics with a lot of manufacturing that went out of business in the 2000's, so that could also be a factor. 

4. The multiple small-medium cities setup in NC seems inherently harder for the new Dem coalition than a state dominated by 1-2 large cities like GA or AZ. 

5.  D's have also struggled vs. (much higher) expectations in VA recently.  Could be something cultural that extends across state lines?

IMO looks much more promising than it actually is.   

[Skill and Chance]

Isn't most of the 'bleeding' product of black depopulation?

No, Dems were getting ~35% of the rural white vote in NC until very recently vs. ~20% or less in the rest of the South.