Agriculture Secretary Tom Vilsack, the former governor of Iowa, will not seek the Democratic nomination for Senate, a Democratic source confirmed to CQ Roll Call.
His decision means Rep. Bruce Braley, D-Iowa, cleared a major hurdle for his party's nod.
Days after Braley entered the Senate race last week, a Des Moines Register poll showed Vilsack in a strong position to run for the seat, boasting plenty of residual good will from his time as governor.
But on Friday, longtime Vilsack aide Matt Paul told the Register that Vilsack "will not seek the open seat."
Sen. Tom Harkin, D-Iowa, announced his retirement last month, creating the first open-seat race for Senate in Iowa in decades.
Several Republicans are also eyeing the race, including Reps. Steve King and Tom Latham.
CQ Roll Call rates the race as Leans Democratic.