(Reuters) - Senate Banking Committee Chairman Tim Johnson, a South Dakota Democrat, does not plan to run for re-election when his current term ends in 2014, sources close to the matter and key Capitol Hill staffers said on Monday.
Johnson, 66, joined the Senate in 1997 and has been widely expected to retire at the end of his term. He plans to make the announcement on Tuesday, the sources said. Johnson's staff said that he will hold a press conference at the University of South Dakota on Tuesday.
His retirement would leave a vacant seat in a conservative-leaning state that could be difficult for Democrats to defend as they try to protect their majority in the Senate.
Political analysts expect Johnson's son, Brendan Johnson, who is South Dakota's U.S. attorney, to emerge as a potential Democratic candidate in the 2014 election. The younger Johnson has not announced any formal plans to seek the Senate seat.
Former Representative Stephanie Herseth Sandlin, who lost a bid for reelection in 2010, is another leading choice to run if the incumbent senator retires.
Johnson's exit from Congress would also create an opening at the top of the banking committee, which he has led since 2011. Currently, Rhode Island Senator Jack Reed is the second-ranking Democrat on the panel.
Johnson told Politico last week that he would make an announcement on Tuesday and reveal his plans for 2014, but he did specify if he would retire or not. A spokesman for the senator declined to comment on Monday.
Johnson joined the Senate after a decade representing South Dakota in the U.S. House of Representatives. He has faced physical challenges following a blood vessel bursting in his brain in 2006, which has noticeably slowed his speech. He went through physical and speech therapy.
Democratic senators Tom Harkin of Iowa, Carl Levin of Michigan, Frank Lautenberg of New Jersey and Jay Rockefeller of West Virginia have already announced plans to retire when their terms end. Republicans Saxby Chambliss of Georgia and Mike Johanns of Nebraska also have said they will not run for re-election.
Overall, 35 of the 100 Senate seats are up for election in 2014, of which 21 are now held by Democrats and 14 are held by Republicans. The Republicans need a net gain of six seats to take control of the chamber.
(Reporting By Margaret Chadbourn and Rachelle Younglai; Editing by Sandra Maler and Alden Bentley)