"It is wrong for anyone to pursue this campaign in such negative and personal terms," Samantha Power, a professor at Harvard's Kennedy School of government and an adviser to Obama said in a statement. "I apologize to Senator Clinton and to Senator Obama, who has made very clear that these kinds of expressions should have no place in American politics."
Power's apology came shortly after the The Scotsman newspaper published an article in which she makes the characterization (a comment she immediately tried to retract), and suggested the New York senator is trying to deceive voters.
"She is a monster, too – that is off the record – she is stooping to anything," Power was quoted as saying.
"You just look at her and think, 'Ergh,' " Power also said. "But if you are poor and she is telling you some story about how Obama is going to take your job away, maybe it will be more effective. The amount of deceit she has put forward is really unattractive."
Power also said the Obama campaign "f***** up in Ohio." Clinton beat Obama by 10 percentage points in Ohio on Tuesday.
"In Ohio, they are obsessed and Hillary is going to town on it, because she knows Ohio's the only place they can win," Powers said.
Obama spokesman Bill Burton distanced the campaign from the remarks, saying in a statement that the Illinois senator "decries such characterizations which have no place in this campaign."
The interview came the same day a top Clinton adviser compared Obama's recent actions to independent prosecutor Kenneth Starr, who prosecuted the Clintons while Bill Clinton was in the White House in the 1990s.
"After a campaign in which many of the questions that voters had in the closing days centered on concerns that they had over his state of preparedness to be commander in chief and steward of the economy, he has chosen instead of addressing those issues to attack Senator Clinton," Clinton's communications director Howard Wolfson said on a conference call with reporters Thursday morning. "I for one do not believe that imitating Ken Starr is the way to win a Democratic primary election for president."
Obama's campaign quickly denounced that comment.
UPDATE: On a Friday morning conference call with reporters, the Clinton campaign called on Obama to end Power's role with the campaign. "Personal attacks are not the way to convince voters that you're capable of being president of the United States,” said New York Rep. Nita Lowey, a Clinton supporter. “We're calling on Senator Obama to make it very clear that Samantha Power should not be part of this campaign.”
- CNN's Alexander Mooney and Rebecca Sinderbrand