Mississippi Doper here. I’d say that it’s very unlikely, but it may happen if Cochran steps down or Wicker gets primaried, and the Republican nominee ends up being Chris McDaniel, who is our version of Roy Moore. (I don’t know of any McDaniel-related sex scandals, but it’s quite plausible that he has some that we don’t know about yet, and he is a terrible, terrible person who got one of his minions to break into a nursing home and take unauthorized photos of Cochran’s wife, who was a dementia patient, the last time he tried to run for Senate. He also picks fights with constituents on social media and generally tries to out-Trump Trump, which isn’t really a persona that plays well with the majority of voters here.)
The demographics are tough. Mississippi is roughly 40% minority, but the white vote is very inelastic, without the big population of college-educated suburban professionals that have turned other southern states purple. Young people have a tendency to leave after they’ve completed their educations, and I can’t blame them. While there have not been the sort of DMV-closing shenanigans we saw in Alabama, MS does have voter ID laws, as well as some other structural barriers to voting (it’s very difficult to access accurate information about voting and registration online, for example, and also to vote absentee).
That said, there is a major grass-roots push going on right now to get people registered to vote (nonpartisan, but particularly focused on college students and African-Americans), and just based on what I’m seeing on the ground, there is a LOT more liberal and progressive activism going on than there was prior to the 2016 elections, when the general attitude tended to be “well, we can’t do anything about Mississippi, so we’ll just let the rest of the country save us from ourselves.” Once it becomes clear no one else is going to save you, you focus on Mississippi.
At the moment, there are serious Democratic challengers in two of the state’s three Republican-majority Congressional districts, which should help somewhat with races higher up on the ballot, but what we don’t have is a strong challenger for the Senate seat. (Jensen Bohren, the only person who has filed on the Democratic side so far, is basically a far-left fringe candidate, and I doubt he’s got the political skills or the funding to mount a serious campaign.) So, basically, we’d need a candidate AND several lucky breaks.