(CBS) -- What's going on in Mississippi?

GOP Sen. Thad Cochran, who has been in Congress since 1973, announced Monday he is resigning from office on April 1st due to poor health. That means that there will be one more U.S. Senate election this November -- and one more chance for Democrats to pick up a seat. Democrats currently control 49 seats in the chamber against the Republicans 51, meaning that this new special election could tie the Senate, though Republicans would still have a one-vote advantage because the vice president, a Republican, breaks any 50-50 tie.

But isn't Mississippi a very Republican state?

It is, yes. However, Democrats just won a special election for the Senate in neighboring Alabama, and there's a possibility they could win this one as well.

How would that work?

Under Mississippi law, the governor, in this case Republican Phil Bryant, will appoint someone to replace Cochran. A special election for the seat would then take place on November 6th, the same day as midterms nationwide, and the winner will stay in office for the remainder of Cochran's term, which ends in 2021.

Bryant would presumably appoint someone who wants to run and keep the seat. But the special election will be a nonpartisan one, meaning that there will be no primary for either party, and party identifications won't be included on the ballot. If no candidate gets 50 percent of the vote in the special election, the top two finishers would then head for a runoff.

OK, but why would the Democrats have a shot?

First, remember what happened in Alabama, where Democrat Doug Jones beat Republican Roy Moore in December. Then remember that Mississippi, while being a deep red state, is somewhat less Republican than Alabama.

This is due in large part to Mississippi's African-American population, which makes up roughly 38 percent of the state and reliably votes Democratic. So while President Trump won Alabama in 2016 by 28 points, he only won Mississippi by 18 points. In 2012, Mitt Romney also did significantly better in Alabama than he did in Mississippi.

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