Sen. Barbara Blackmon of Canton, a Democrat, is running for lieutenant governor. She made the announcement Wednesday.
Blackmon, 47, is a lawyer and has been in the Mississippi Senate since 1992.
Former state Supreme Court Justice Jim Roberts of Pontotoc and former Cong. Ronnie Shows of Bassfield also are considering running as Democrats for lieutenant governor.
Lt. Gov. Amy Tuck was elected as a Democrat in 1999 but switched to the Republican Party in December. She is seeking a second term.
Ridgeland eye doctor Randy Russell is running as a Republican.
Candidates' filing deadline is Mar. 1. Blackmon is the tenth senator not to seek reelection this year.