A KEY advisor to Barack Obama quit overnight after calling Hillary Clinton a "monster'' and sparking a new Iraq war policy row, as the hyper-competitive Democratic White House race took another nasty twist.
A day ahead of the next showdown, the caucuses in the western state of Wyoming, the Clinton camp crowed it was "amateur hour'' in the Obama campaign's foreign policy team, after Pulitzer prize winner and Obama foreign policy advisor Samantha Power's explosive remarks during a book tour in Britain.
The episode suggested the frustration in the Obama camp after the former first lady's comeback wins in Ohio and Texas on Tuesday revived her campaign.
"We f***ed up in Ohio,'' Ms Power told the Scotsman newspaper.
"In Ohio, they are obsessed and Hillary is going to town on it, because she knows Ohio's the only place they can win,'' Ms Power was quoted as saying.
"She is a monster, too - that is off the record - she is stooping to anything,'' Ms Power said.
"You just look at her and think, 'Ergh.'''
Ms Power afterward issued a statement through the Obama campaign saying she was sorry, but Ms Clinton's backers pounced in a conference call, and her resignation came within two hours.
"I made inexcusable remarks that are at marked variance from my oft-stated admiration for Senator Clinton and from the spirit, tenor, and purpose of the Obama campaign,'' Ms Power said when she resigned.
Ms Power, author of the acclaimed book A Problem from Hell: America and the Age of Genocide, also caused a stir in an interview with the BBC in which she appeared to suggest Mr Obama might water down a vow to get US combat troops out of Iraq within 16 months of becoming president.
"He will of course, not rely on some plan that he's crafted as a presidential candidate or a US senator,'' said Ms Power in the interview.
"You can't make a commitment ... in March of 2008, about what circumstances are going to be like in January 2009.''
Former US State Department spokesman and Ms Clinton advisor James Rubin said Ms Power had been exposed by inadequacies in the Illinois senator's foreign policy apparatus.
"I feel sorry for her, that she has been put in a position where he can't run a foreign policy team,'' Mr Rubin.
"It's the man at the top who has not organised himself.''
But Mr Obama attempted to clarify the situation.
"Senator Clinton used this to try to imply that I wasn't serious about bringing this war to an end. I just have to mention this because I don't want anybody here to be confused,'' he said while campaigning in Wyoming.
"It was because of George Bush with an assist from Hillary Clinton and John McCain that we entered into this war.''
"I have been against it in 2002, 2003, 2004, 5, 6, 7, 8 and I will bring this war to an end in 2009.''
Mr Rubin tied the affair to the row last week over the North American Free Trade Agreement (NAFTA) when the Obama campaign was accused of telling Canada their candidate's fierce anti-NAFTA rhetoric was for political positioning.
"It's amateur hour on making foreign policy,'' said Mr Rubin.
Mr Obama's campaign manager David Plouffe however said Mr Obama's Iraq war vow was a "rock-solid commitment.''
The latest nasty twist to the campaign came as a new poll showed the two deadlocked in their epic battle to represent the party in the November 4 presidential election.
A national Newsweek poll released Friday showed the two in a virtual tie among Democratic voters, with Mr Obama with 45 per cent support against Ms Clinton's 44 per cent.
The two were also virtually equal in voters' eyes on the issue voters see most important: the sagging economy.
Ms Clinton and Mr Obama will tonight face down in Wyoming, which offers only 12 delegates - a candidate needs 2025 to clinch the party's nod - and on Tuesday, the more significant Mississippi primary, with 33 delegates.
Mr Obama is favored in both, but with his current delegate count at 1581 to Clinton's 1460, according to the independent website RealClearPolitics, neither contest will settle the fight.