Rep. Tom Latham (left), Iowa Republican, has declined to run for the U.S. Senate seat being vacated by Democratic Sen. Tom Harkin. Reps. Bruce Braley (center), a Democrat, and Steve King, a Republican, have shown interest in the seat. (AP Photo/File)

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Rep. Tom Latham (left), Iowa Republican, has declined to run for the U.S. Senate seat being vacated by Democratic Sen. Tom Harkin. Reps. Bruce Braley (center), a Democrat, and Steve King, a Republican, have shown interest in the seat. (AP Photo/File)