Romney's redeployment of assets from NC seems like a reasonable calculation, given his needs elsewhere and apparent strength here1. My (entirely unscientific) analysis of the Mittenization of our state includes: Residual energy and organization among conservatives after the May primary vote on Amendment 1, and possible erosion of enthusiasm for a newly pro-gay-marriage Obama among black voters in the wake of same; stubbornly high unemployment; a gubernatorial race in which GOP candidate Pat McCrory seems a near-inevitable winner2; the slow and to a meaningful degree self-inflicted death of the old Democratic machine; and frustration among Democrats who see the new GOP-drawn voting maps creating insurmountable odds.
1Obama's ground game made the difference here in 2008, but by the thinnest of margins. If his team can repeat the feat this year, someone should write another case study.
2I'd guess that a lot of Democrats are pretty comfortable with the assumption that McCrory, a sensible Guilford County native, will govern more like he did as Mayor of Charlotte and less as the hard-liner he's pretended to be on the campaign trail. Ditto for Romney, for that matter.