The idea that Mississippi would be a leans McCain state rather than a solid McCain state in the event of Barack Obama being the Democratic nominee seems to me to be based on an ambiguity in the idea of leaning.
I imagine that with Obama as the nominee, you’ll see him get an incredible performance from Mississippi’s black population, and because that population is so large the result would probably be tighter than the 60-40 split that John Kerry got. So maybe it’ll “lean” McCain and wind up as only a 55-45 state or something. But there’s just no way that Obama will ever win Mississippi. The southern states with larger black populations just have more racially polarized voting. At the end of the day, most Mississippians are white, they’re not going to let Obama win the state, and you can take that to the bank.