I don't think it's that brilliant at all. He's going to get destroyed for not having said it himself and then why he had to go through multiple surrogates. It's something that the Obama coalition hates and any attention towards it puts Trump on the defensive.
Or...
Hillary can ignore it, honestly.
He hasn't said it himself, and she can keep repeating that (as well as other Democrats) he was the main birther for years. Because it honestly doesn't matter if Trump now personally believes Obama was born in the U.S., and I bet most Americans imagine he believes Obama is born in the US, or don't care what he believes now. They aren't letting him off the hook, but the Trump Campaign is trying to make this about a simple statement, but it isn't about that.
He questioned Obama's legitimacy, character and ended up looking stupid. That won't change, and the Clinton camp and Obama know this and they won't give a shit if he personally says he "believes" the President was born in the U.S. Trump is trying to lower the bar of the debate to whether he personally says it now or not, when the problem has never been that.
It has always been that he hounded the first black president for years about being "foreign" and illegitimate, and it doesn't matter what he does now just a month and a half before the election.