There seems to be evidence that his father was not an American citizen.
That BHO’s father was not an American citizen is an indisputable fact.
What this means in regards to BHO’s own citizenship status is another matter.
IF BHO was born abroad, then there might be an argument.
But he was born in Hawaii. And when a person is born on US soil to an American mother, they are a natural born citizen. Some folks disagree with this assertion, but I do not find their arguments compelling.