Obviously someone can change sides and change their opinion of things. I don't think hypocracy and inconsistency are that bad -- neither is a substantive sin, certainly. They've only become such great sins in our culture because we've lost any sense of basic values. When everything is relative, consistency is the only thing that can be judged.
So sure, given new facts and personal analysis of those facts you can change sides -- and it's certainly better to change sides then to knowingly hang onto incorrect beliefs. I don't advocate blind partisanship. But I don't think it's very effective to try to reach conclusions as events unfold, and I don't think it's constructive to analyze every detail of events. At some level we must place some faith in a leader (not necessary a political leader).