He was born to a US citizen mother, in the United States. Therefore, he is a natural born citizen. And whether you or I like it or not, there’s not the slightest doubt about his status.
Based on what? The circumstances of his birth fail to meet the requirements of the 14th Amendment for birthright citizenship. He was subject to a foreign power at birth. U.S. Secretaries of State have confirmed that such a circumstance of birth precludes birthright U.S. citizenship.
Furthermore, he fails to meet the named conditions for birthright citizenship in U.S. v. Wong Kim Ark. His father wasn't permanently domiciled in the U.S. in 1961, or ever.
And whether you or I like it or not, there’s not the slightest doubt about his status.
For at least the reasons I've stated, there is SIGNIFICANT doubt about his eligibility status. Obama is NOT eligible, plain and simple. Legally, he isn't even a U.S. citizen unless he naturalized at some point.
Among liars and fools. Among reasonable and truthful people, there is a great deal of doubt about his legitimacy. It is compounded by the fact that he makes such great efforts to obfuscate it.