This was at an annual dinner in which the candidates roast themselves & the other opponent, mostly themselves and yes, at some point during the evening Obama said he could have been Steve, but not in any context that would have connected it to the birther file of evidence.
I saw the entire video when it 1st aired in 2008 & it was hillarious. Obama totally fell flat on his face, while McCain took down the house.
This is a VERY early developing story so far as I know, but I haven't heard anyone discredit that yet.