I'd expect a current poll to read something like...
Barbour: Low fifties
Eaves: Low thirties
Undecided: Mid teens
You're misunderestimating a few things:
--Kerry was a terrible candidate for Mississippi. Eaves will do much better among whites in Mississippi than Kerry did.
--There is a black candidate, Gary Anderson, running for Insurance Commissioner who has a legit chance of winning. He would be the first African-American to ever hold statewide office in Mississippi. He's done a great job campaigning and ought to keep black turnout high, and could end up having some (small) coattails on the rest of the ticket.
--Barbour promised the fundies he'd never let casinos move onto land and then he did. They have not forgiven him for that and many are buying into Eaves's pro-Jesus pro-family stances. Eaves is putting together a bizarre coalition of liberals, blacks, and fundamentalist Christians that may not win, but will at least surprise some people across the country.