Arizona Democrats had hoped that either Rep. Gabrielle Giffords (D-Ariz.) or her husband, astronaut Mark Kelly, would jump into the race. But Giffords is still recovering from an attempted assassination in January, and Kelly said in early July he had no plans to run. Former governor and current Department of Homeland Security Secretary Janet Napolitano has said she will not run for the seat.

On Friday, former Arizona Democratic Party Chairman Don Bivens formed an exploratory committee for the race. He joins businessman David Crowe in the field. Other possible Democratic candidates include Rep. Ed PastorEd PastorWhich phone do lawmakers like the most? CAMPAIGN OVERNIGHT: Political tomfoolery Pastor endorses in race to replace him MORE (D-Ariz.) and current party Chairman Andrei Cherny.