Democratic nominee former Lieutenant Governor, John Carney defeated Republican nominee Glen Urquhart, giving Delaware an all Democratic congressional delegation for the first time since before the 1942 midterms.

Castle announced in 2009 he would run for the United States Senate seat[3] held by Ted Kaufman (D) who had been appointed to the seat when his predecessor, Joe Biden (D), resigned to become Vice President.

Castle was defeated by Christine O'Donnell in the Delaware Republican Senate primary.

Carney announced his candidacy on April 15, 2009, and was unopposed in the primary after Scott Spencer, a transportation consultant, dropped out.

[4][5] According to a September 2010 poll by Fairleigh Dickinson University's PublicMind, "likely voters in Delaware split 45%-40% on whether they prefer[ed] to have the U.S. Congress controlled by the Democratic Party or the Republican Party, suggesting that the First State's open congressional seat might be hotly contested," yet in the same poll, Carney led Urquhart by 51%-36%.