Potential 2012 Republican presidential contender Mitt Romney has endorsed tea party-backed Christine O'Donnell in the race for Senate in Delaware and contributed $5,000 from his political action committee to her campaign.
O'Donnell stunned the Republican establishment Tuesday by defeating veteran Rep. Mike Castle, who had the backing of the state and national GOP, after a divisive primary campaign.
Romney lost the Republican presidential nomination in 2008 and has been using his Free and Strong America PAC to assist candidates nationwide. The PAC last month reported nearly $300,000 in contributions to candidates and political committees.
In making the endorsement, Romney urged Republicans to rally behind O'Donnell, saying she ran an "impressive" campaign.