Sen. Tim Johnson, D-S.D., chairman of the Senate Banking Committee, today announced he would not run for re-election.
Johnson at a press conference in his home town of Vermillion, S.D., said that at the end of this term, it will be "time for me to say goodbye."
His decision establishes former Gov. Mike Rounds, a Republican and an insurance agent, as the likely front-runner to succeed him.
Rounds is considered the frontrunner because Mitt Romney won 66 percent of the vote in a state that has turned increasingly red over the last several years.
If Democrats retain the Senate, Sen. Jack Reed, D-R.I., or Sen. Charles Schumer, D-N.Y., are considered the favorites to succeed Johnson.
If Republicans win, Sen. Mike Crapo, R-Idaho, or Sen. Richard Shelby, R-Ala., would likely become chairman. Crapo succeeded Shelby this year as ranking minority member when Shelby decided to become ranking minority member of that committee.
It is expected that Shelby would become chairman of the Appropriations Committee if Republicans won control of the Senate even though he has served on the Banking panel since coming to the Senate in 1986.