I agree. It is my suspicion that she was there all along. In 1961, I cannot imagine the Family wanting to have her around to give birth to the child of a black man. I think she left Hawaii to stay with relatives (Either Ralph Dunham, or Eleanor Birkebeile, both living in Northwest Washington state at the time) prior to his birth. This was the custom for embarrassing pregnancies of that era.
I have already pointed out how Madelyn Dunham's co-workers were not aware she had a grandchild until they heard he was running for President. Had Madelyn been proud of her grandson (the normal behavior of a grandmother) she would have told her co-workers when he was born, and likely have pictures of him upon her desk. ( I should say most people would.)
The fact that they remained in the dark about his existence implies that Madelyn Dunham was initially uncomfortable with the social stigma attached at this time. She was from Kansas, but lived in Oklahoma and Texas where (at the time) it was a FELONY CRIME to produce mixed race children.
I think Barry was born in White Rock or Vancouver Canada, and only has a weak connection to American citizenship through the actions of his Grandmother back in Hawaii, who filed an at home birth registration with the state.
So far, I know of no evidence which impugns this probability thread.
There isn’t a Washington BC for Obama.