 In the seat's most recent election in 2008, longtime Democratic incumbent Joe Biden defeated Republican Christine O'Donnell.However, Biden was also elected Vice President of the United States in 2008 and was required to resign from the Senate by Article I, Section 6 of the United States Constitution in order to assume the Vice Presidency.Although Biden was sworn in for a seventh term early in January 2009, he resigned from the Senate on January 15, 2009, and was succeeded by Kaufman the following day.