The cameo aired while Obama was behind in the polls to Hillary Clinton. Afterwards, the senator has a fluctuation in his numbers. According to Pollster.com, in October of 2007, Clinton lead Obama 38% to 27%. Two weeks after the SNL episode aired, Clinton gained some cushion with a 45% to 20% lead. Although I do not have significant evidence to conclude the appearance did not boost support, it does raise the question as to will this appearance hurt him?
Sadly enough, Obama may not be present in New York for the show. His campaign advisers have mentioned that if Hurricane Ike continues to southern Texas, his work will displace him there.
Personally, I think revisiting the SNL stage is a very clever and strategic move for the Obama campaign. There is the thought that if a candidate is to visit the Colbart Report or Daily Show, they have gained youth support. I think much is the same for SNL. Obama has banked, figuratively and literally, on the youth voters, so portraying himself as someone who can joke around too will be beneficial.
Although I cannot guarantee he will be dancing with Ellen (check it out on youtube), I have a promising feeling it will be entertaining. In addition, it will definitely be beneficial to reaffirm youth votes and/or gather new ones.