I got the impression that like McCain, you can be born anywhere if at least one parent is a citizen then by birth you are to and THAT was why Obama was ok, the same reason McCain was OK and why Cruz would be OK.
Whether a parent is a citizen by birth is irrelevant. What matters is that they are citizens and the child is born in the US. If citizenship relies upon statute the person is not a natural born citizen.
Again, Obama could not receive citizenship from his mother. There is no evidence that Obama was born on U.S. soil. Consequently, there is no evidence that Obama is a U.S. citizen.