the laws in effect at the time (you know sometimes you have to thread the needle to understand how a law applies to the facts) might well be construed to prove he was not a legal natural born citizen at the time of his birth.
Also, by getting the story out there, and planting the seed that he might not be a bona fide natural born citizen, taken together with his questionable radical associations, should be able to do some collateral damage for voters in the mushy middle.
0bamy’s mom has been conspicuously absent this whole time.