Sen. Joe Biden will pursue two campaigns at once this fall: his race for the White House as Barack Obama's running mate and his quest for re-election to the Senate.

Biden spokesman David Wade said Sunday that Biden will continue his Senate re-election campaign. Biden is expected to defeat Republican challenger Christine O'Donnell in November.

That means that if Obama and Biden win the presidential race, Biden's Senate successor would be appointed by the Delaware governor. The governor's race is also on the ballot this November.

"I hope we get that opportunity," said Lt. Gov. John Carney, a former Biden staffer who is seeking the Democratic nomination for governor.

It could fall to the current governor to choose a Biden successor. Democratic Gov. Ruth Ann Minner is barred from seeking re-election, but could still be in office after the new president and vice president are sworn in at noon on Jan. 20, by which time Biden would have to officially relinquish his Senate seat. Delaware's new governor also will be sworn in that day.

If the governor's inauguration comes after noon, Minner could choose an interim replacement for Biden as one of her last acts in office. If not, her successor would make the appointment.

"It's too early to start worrying about that," Minner said.

Among those considered possible appointees to hold Biden's seat until an election could be held is his son Beau, who was elected state attorney general in a 2006 campaign seen by many political observers as a stepping stone to higher office. But the younger Biden is scheduled to join his National Guard unit in October ahead of a deployment to Iraq that could last up to a year, and it's unclear whether a deployment would prevent him from taking the Senate seat.

Other names that have surfaced as potential fill-ins for Biden's seat are Carney and state treasurer Jack Markell, who are competing for the Democratic gubernatorial nomination in a primary battle that Delaware Democrats had hoped to avoid. Some fellow Democrats are wondering whether Carney or Markell might be persuaded to drop out of the primary if guaranteed the spot as Biden's replacement, but neither seems willing to entertain the idea.

"I'm totally focused on winning the primary," Markell said.

Democrats outnumber Republicans in Delaware, so the winner of the Democratic gubernatorial primary likely will be favored over the winner of the GOP race between Bill Lee and Michael Protack. Protack is also running as the Independent Party's candidate.

___

Associated Press Writer Sharon Theimer in Washington contributed to this story.