I don't think the torture issue suddenly came up when he became President. There was plenty of discussion about that while Bush was POTUS. Seems like the only thing that Obama has added is to try to deal with the whole issue of whether there will be any sort of prosecution of those who waterboarded or sanctioned it.
Obama is in a tough spot on this because the reality is that a huge percentage of the American people, and they may in fact be the majority, do not object in principle to torturing terror suspects. In fact, a bunch support it.
Now, they may say that their reasoning is that waterboarding is not torture. In reality, they don't care if it is.
This is not to say that they would support all forms of torture. I am sure there are things that even those who support waterboarding would simply not be able to stomach.
But the political reality is that a lot of people don't have a problem with it whereas it is at least rhetorically inconsistent with his campaign message . I think that is why he has waffled on it so.