I think the direct results of it failling will be minimal, as it would look that he spent all his effort and time on something that left him holding an empty sack. Not to mention it was unpopular with the american public. It'll end up being used as part of a narrative by the romney camp about how obama was an ineffectual president. The reaction romney will look for is "you spent all your time on something we didn't want, the supreme court said no, and what do you have to show for it?"
Soo I dont think his numbers will drop as a direct result, but it will be used as part of a narrative by the romney camp.