[wtc911]

Proof of citizenship is....the most frequently used proof is a birth certificate...what did obama use?

[Calpernia]

I don’t know what he used. I do know that a birth certificate is NOT needed to get a passport. Null and Void has posted the link to the state site repeatedly telling of the procedure to obtain one without a birth certificate.

Also, a family passport can be used per this post:

http://web.israelinsider.com/Articles/Politics/12993.htm

In the comments by a poster named muzhik:

Obama may never have had to produce his birth certificate to get a passport. As a baby, he would have been included in his mother’s passport as a “family passport”. Whoever took her application may not have required her baby’s BC — it’s the ‘60s, she’s white, the daddy’s black, and it’s not like the kid will ever run for president. Sloppy by today’s standards, but not necessarily by the standards of the time.

After that, it’s just a matter of keeping the passport renewed. When he turned 14, Obama would have gotten his own passport, using the “family” passport as proof of citizenship. If he kept his passport renewed, he never would have needed to produce a certified birth certificate.

[bvw]

It would be helpful if he told us what he used. That would perhaps enable some review and discussion of our government is performing in that regard. It would also indicate that he's a open honest fellow.

Still, the direct answer to your question is nobody knows. We don't know. Why do you ask?