1. I, Trump decide when and how we discuss the legitimacy of the occupant of the White House. That puts me above Barack Obama and makes me” presidential” in your mind. I do not need the birther issue anymore. By admitting this now to appeal to voters on the fence, I need to fill in a couple of cognitive gaps for my supporters, so
2. If anyone thinks my actions could be an affront, please be aware this was a huge service I gladly provided, and
3. My claim about Obama was an accusation. By retracting it, I need to replace it in your mind with a new accusation that it was all Hillary’s idea. That shifts my finger pointing from my earlier target to my current target. Clinton’s attacks on my birther behavior which would have been given new life by my retraction of the lie (never called a retraction because I am never wrong and never apologize) are thus watered down and require her and her supporters to mount yet another defense.
If Trump had said, “I did nothing wrong”, that statement puts a bright light on the possibility there was wrongdoing on his part. Doubling down makes him look strong.
This faintly echoes the GW Bush defense of the Iraq invasion during the 2004 campaign - Senator Kerry voted for the resolution, so that offsets the Bush decision to invade. If you agree with the decision to invade, then vote for the president who ordered it, but if you disagree with the decision, then surely you should not vote for the Senator who supported the authorization resolution. The inherent contradiction of this position is not a concern, because ending the possibility of any rational discussion of the issue is an important objective.
Laboring under the false balance model, the press has a really tough time depicting reality ---and should admit it! No, it’s not a bias toward making money, not directly, but there is a bias toward new news. The press model requires all of the above statements to be labeled opinion that is not allowed to seep into “news” coverage, thus letting the Trump/Conway/Ailes propaganda machine get away with it and roll on.