Former Gov. Mike Rounds, a Republican, will make an announcement Thursday about the race against Democratic Sen. Tim Johnson.
Local news outlets reported Rounds will jump into the race during a three-stop tour of the state. A press release did not specify his intentions.
Rounds announced weeks ago that he was exploring a bid for the Senate seat. A two-term governor, Rounds' candidacy makes the South Dakota race competitive.
What's more, Johnson has not said yet whether he's running for another term. If Johnson retires, Rounds will have a head start on the other candidates in the race.