New Mexico Gov. Bill Richardson, a former presidential candidate, has endorsed Barack Obama.
That leaves another former contender, John Edwards, and former Vice President Al Gore as the biggest endorsement possibilities left to Obama or Hillary Clinton:
Richardson, who dropped out of the Democratic race in January, is to appear with Obama on Friday at a campaign event in Portland, Ore., The Associated Press has learned.
The governor's endorsement comes as Obama leads among delegates selected at primaries and caucuses but with national public opinion polling showing Sen. Hillary Rodham Clinton pulling ahead of him amid controversy over statements by his former pastor.
Richardson has been relentlessly wooed by Obama and Clinton for his endorsement. As a Democratic superdelegate, the governor plays a part in the tight race for nominating votes and could bring other superdelegates to Obama's side. He also has been mentioned as a potential running mate for either candidate.