Sen. Tim Johnson, D-S.D., chairman of the Senate BankingCommittee, has announced he will not run for re-election.

His decision establishes former Gov. Mike Rounds, a Republicanand an insurance agent, as the likely frontrunner to succeedhim.

Rounds is considered the frontrunner because Mitt Romney won 66percent of the vote in a state that has turned increasingly redover the last several years.

Tom Santos, American Insurance Association vice president forfederal affairs, said, after Johnson announced his decision at apress conference, "We have greatly enjoyed working with Sen.Johnson in his capacity as chairman of the Senate Banking, Housing& Urban Affairs Committee. Sen. Johnson has a long record ofsupporting a healthy and competitive insurance marketplace and welook forward to continuing to work with him on issues important tothe industry in this Congress."

Jimi Grande, senior Vice President of federal and politicalaffairs for the National Association of Mutual Insurance Companies,said, "As he announces his retirement, NAMIC congratulates Sen. TimJohnson for his years of public service."

 Grande said Johnson has been a "champion for SouthDakota and consumers across the country.

"His deep understanding of the issues and willingness to workacross the aisle were vital  to seeing passage of majorreforms to the National Flood Insurance Program, and will be againas we seek reauthorization of the Terrorism Risk Insurance Act.

"We are grateful for his service and wish him the best as heleaves the Senate," he said.

If Democrats retain the Senate, Sen. Jack Reed, D-R.I., or Sen.Charles Schumer, D-N.Y., are considered the favorites to succeedJohnson as chairman of the Senate Banking Committee.

If Republicans should win the Senate, Sen. Mike Crapo, R-Idaho,or Sen. Richard Shelby, R-Ala., would likely become chairman.

It is expected that Shelby would became chairman of theAppropriations Committee if Republicans won control of the Senateeven though he has served on the Banking panel since coming to theSenate in 1986.

Top Democratic candidates for Johnson's seat are his son,Brendan Johnson, 37, and former U.S. Rep. Stephanie HersethSandlin. Brendan Johnson has served as U.S. attorney for SouthDakota since 2009. But the appointment was controversial becauseconcerns were raised about his father's involvement in the process,South Dakota officials have indicated.

Johnson, 66, has been in Congress since 1986. He was elected tothe Senate in 1996, and re-elected twice.

Johnson suffered a brain hemorrhage at work on Dec. 13, 2006,and underwent emergency brain surgery, a medically induced coma andmonths of grueling physical, occupational and speech therapy beforereturning to the Senate nearly nine months later.