I always thought it was strange that Mecklenberg is more Democratic (by a significant amount) than Wake. Just looking at the Demographics and population you'd think Wake would be the Democratic stronghold and Meck would just be a lean Dem county, but they're both becoming Dem strongholds.
I think Mecklenburg is more Democratic than Wake because Charlotte contains a larger share of Mecklenburg's population (79.8%) than Raleigh's share of Wake's (44.8%). Raleigh is probably more liberal than Charlotte.
Living in Chapel Hill, and having lived in Raleigh, both those points make sense. Locally, Charlotte is thought of as being pretty conservative, even if the recent numbers (Pres. and Amendment One in 2012) haven't confirmed that. Certainly the Triangle as a whole is way more liberal than the Charlotte metro, though Orange and Durham are part of that. Still, Raleigh appears to be more liberal than Charlotte.