Maybe she's not apologizing because she doesn't think that vote was in fact a mistake based on what information they were given by the White House at the time. Were they supposed to be mind readers and automatically tell that the Bush administration and intelligence officials were lying about Iraq having weapons of mass destruction? Were they supposed to be able to read Bush's mind and automatically know about this whole other agenda? Every one of those senators who voted for this authorization were played for fools, but is that their fault? Or is it Bush's?

Hillary seems to be saying that it is Bush who needs to apologize, not her or anyone else who voted in the Senate. He knew the truth, they didn't. A leader stands behind his/her votes, regardless of whether they were right or wrong. A leader doesn't apologize and say "whoops I'm sorry" the minute public opinion changes in the other direction. That is what Edwards is doing. Hillary is taking the more principled position, she regrets her vote but she won't apologize for it, she'll stand behind it right or wrong.