Iowa Gov. Terry Branstad has set a special election for Dec. 27 to fill the state Senate seat left open by the death of Sen. Joe Seng, D-Davenport.Meanwhile, two Democratic lawmakers, Reps. Jim Lykam and Cindy Winckler, said Wednesday that they plan to seek the party’s nomination for the seat.Seng, who was not on the ballot this year, died last Friday after a two-year battle with brain cancer.