A. C. Kleinheider and Bo Heyward make a good point.
If you changed your position on the war, either admit that you were wrong in the first place, or explain why things have changed so that your old position is no longer correct; there is no shame in saying "I supported the removal of Saddam Hussein, still do, but we did what we needed to do and now we need to get out. I supported the war, I don't support continuing it any longer, though, now that Saddam is out of power." Alternately, there is some shame, but only a little, in saying "I was wrong before. We should not have gone into Iraq. Let's get out, now."
But saying "we were wrong to get into war with Iraq. But it's not my fault," is a gross passing of the buck.
That is why Kerry was called a flip-flopper. Not because he changed his mind, but because he simply claimed whatever position would be politically advantageous to him at the moment.
That is all.