What I learned years ago about the 'natural born' requirement for President must be totally wrong but I shall try and remember the highlights and put them out for comment.

The Founding Fathers in order to secure the 'highest office ' in the land from any person who might have divided loyalties becoming President required he be  'natural born'.

The Constitution does not define 'natural born'; that which is not clearly defined refers back to English 'Common Law' and usage.

In the 1700's the common way of determining an infants citizenship was by 'Blood Passage or Blood Rite'; what the father is so are the children. A Frenchman marries an English woman and they reside in England, their children would be considered French.

The Congress of the United States over the years has legislated various ways that an individual is a citizen, being born on American soil (native born), having an American mother ( I believe the early 1800's, before woman's suffferage and equal rights), having an American parent (the "anchor babies') are some of these but 'natural born' refers to the father.

With 'Equal Rights' and keeping in mind the intent of the Founding Fathers to protect the presidency from the possibility of divided loyalties the 'natural born' clause would evolve to the point that both parents would have to be citizens.

Obama is a citizen by virtue of being born in the U.S. (native born); so are many whose parents are illegal aliens.

Obama is a citizen by virtue of the fact his mother is an American citizen.

Obama is not a 'natural born' citizen by virtue of the fact that his father was a Kenyan.

 

Obama has been referred to as 'the Kenyan with American credentials' by at least one foreign leader.