Several possible options:
He was not born in this country.
His father is not who he has said he is.
His mother is not who he has said she is.
He was born in this country but, as part of a family that emigrated to Indonesia, renounced their citizenship.
He ‘claimed’ his Kenyan/Indonesian citizenship to avoid the SS registration and get a foreign passport - traveled to Pakistan and got Manchurianized.
He lied about any or all of the above to fraudulently obtain educational assistance at one or more institutions.
There is a reason this man and his handlers have exhausted a lot of capital (financial and journalistically)to keep the answers to these and other questions off the table. Trump, as much as I might dislike him, has good reason to reinvigorate this question. Ultimately, it is a trivially simple thing to exhibit a real birth certificate to bring all questions to close.
Publicly insinuating he is a fraud.
This is a sight to behold.
The last time we saw something like this, it was Dan Rather accusing Bush of going AWOL.