The only interview I’ve ever seen where Obama answers the question (from 2004):
http://www.patheos.com/blogs/thedudeabides/obama-on-faith-the-exclusive-interview/
That interview took place at 3:30 p.m. on Saturday, March 27, 2004 and does not contain what can remotely be called a Christian testimony. He refers to the “Christian tradition” and that his solid white mother was “a Christian”.
No testimony there.
Why not ask 0 in front of witnesses now if he prefers Jesus Christ (the Reason for Christianity) over Muhammad and Islam?
What could it hurt? He’s not running for office now, is he...?
GG:
Do you believe in sin?
OBAMA:
Yes.
GG:
What is sin?
OBAMA:
Being out of alignment with my values.
In other words, no, he does not believe in sin. Because if you think something is a sin you simply change your values and poof...no more sin! Sin, ultimately, is transgression of God's law.