First of all, I do not want to discredit the seller at all. If he says it is authentic, you can make your own judgement. Im just going to tell you what I know.
I have seen thousands (literally) of pictures of Obamas autograph. I own four myself, two of which are PSA DNA authenticated. This does not look authentic at all.
I have been to 6 Obama rallys. I was extremely close at three of those. Every time the secret service came out and collected only books for Obama to sign backstage. When Obama would come to shake hands after the rally, he did not sign at all and would even point to the books for the secret service to grab so he could sign backstage. They would not take photos, rally signs, or baseballs...only books.
I can almost guarantee that this would not pass PSA DNA quick opinion service.
Pantherfan2, if you originally purchased this from someone else, you probably paid big bucks for it. I would try to get a refund.