Mississippi is 40% African-American (the highest % in the country if I'm not mistaken). If African American voter-participation rate goes up, it would turn into a blue state. But it probably won't happen in 2018. It doesn't hurt to try of course.
Even if Blacks turn out according to their share in the population (40%) and Espy wins all of them, he would still need some 15-20% of Whites to win ... which is hard in MS.
This is actually the bigger problem: if whites in Mississippi even voted like whites in Oklahoma, it would be a Blue State.