WATERLOO, Iowa (AP) -- Potential candidates for U.S. Sen. Tom Harkin's seat began to emerge Sunday, one day after the Iowa Democrat announced he would retire.

Harkin told The Associated Press in an interview Saturday that he won't run in 2014 for a sixth term in the Senate, where he has served since 1985.

Democratic U.S. Rep. Bruce Braley said Sunday that he is considering running for Harkin's seat because supporters statewide have encouraged him to do so.

Most of the other likely candidates kept a low profile on Sunday.

Braley, a 55-year-old Waterloo attorney, was first elected to represent northeast Iowa in 2006.

"Iowans deserve a senator who will continue Tom Harkin's legacy of strengthening the middle class and standing up for Iowans who don't have a voice," Braley said. "While Sen. Harkin's shoes are impossible to fill, over the coming days my family and I will carefully weigh a possible candidacy for Senate."

Harkin said Saturday that he might endorse a Democrat in the primary if there was a "pragmatic progressive" candidate.

And Braley could give Democrats a shot at retaining control of the Senate. Republicans must gain six seats to eliminate Democrats' 55-45 advantage in the chamber. Retaining control could be difficult because Democrats have 20 seats to defend, while Republicans have only 13 to defend.

Harkin's decision to retire will give the Republicans an opportunity to win the seat in a swing state like Iowa.

The Republican speculation is likely to focus on U.S. Reps. Tom Latham and Steve King.

Latham, of Clive, is a veteran member of the House Appropriations Committee who has won 10 consecutive elections. Latham's office didn't rule out a run for the Senate on Sunday.

"No decision has been made at this time. All doors remain open at this point," said James Carstensen, Latham's chief of staff.

Rep. Steve King, of Kiron, won a sixth term last fall by beating Iowa's Democratic former first lady Christie Vilsack. King's office did not immediately respond to a message Sunday afternoon.

King is known for being an outspoken conservative with strong positions on everything from immigration to the federal budget.