I don't think Team Obama was counting on NC, even before the marriage equality issue. He won it in 2008 by only 14,000, I believe.
But to take the other side of the argument, remember that NC is lousy with retired military who most likely voted for fake war hero John McCain. None of Bishop Romney's clan have ever served their country (I'm talking U.S.,
not Mexico), while Commander In Chief Obama has been a killing machine against al Qaeda.
PLUS, NC is also lousy with fundamentalists and Southern Baptists (redundant, I know), who believe Bishop Romney is a cultist (he is!). Those who actually believe in their religion and their values may stay home.
Of course, we know that people will gladly throw their religion under the bus for an extra dollar, so who knows?