Democrat Scott Colom and Republican incumbent Republican Cindy Hyde-Smith were locked in a surprisingly close race that ABC News had not projected as of Wednesday.
With most of the vote in, the difference between Colom and Hyde-Smith was less than 100 votes. Mississippi allows mail ballots that arrive up to five business days after the election, the the secretary of state's office said it couldn't put a number on the how many outstanding votes there might be.
Mississippi does not have a recount process, the secretary of state's office told ABC News, meaning candidates can't request a recount and there is no mechanism to trigger one in a tight race. Mississippi's deadline to certify its election results is Nov. 13.
See live election results below: