Delaware State Republican Party Chairman Tom Ross, once one of Senate nominee Christine O'Donnell's biggest critics, called on his party Thursday to unify around her campaign.

O'Donnell on Tuesday pulled off a stunning upset over centrist Rep. Mike Castle in the Senate GOP primary. Castle had the endorsement of the state party, which aggressively attacked the Tea Party-backed O'Donnell during the campaign. Ross had previously said that O'Donnell is not a "viable" candidate for office and "could not be elected dog-catcher."

"After a hard-fought primary, it is time to come together and unite over our shared principles and determination to rescue our economy from the destructive policies advanced by Democrats," Ross said in a statement. "The Delaware Republican Party plans on doing what it does every election year — working hard for our candidates."

Ross joined other Republican leaders in circling the wagons around O'Donnell's candidacy after negative reactions to her victory from some party officials.

Former Bush senior adviser Karl Rove, among others, had said that O'Donnell would not fare well in the general election against Democratic nominee Chris Coons because of her controversial past statements. Fox News also reported Tuesday that the National Republican Senatorial Committee (NRSC) would not contribute funds to her campaign, but Chairman John Cornyn (Texas) later said it would.

Ross said the state party has "reached out to the NRSC, NRCC [National Republican Congressional Committee] and RNC [Republican National Committee] to ensure that our candidates have as much support as possible."