The only way any poll would return 50% support for Obama is if it was conducted at the welfare line, prison, gay parade, public housing project, or any other non-mainstream America location. I am not saying Obama can't win (with the mass media fully behind him anything is possible), but these polls are pretty meaningless at this point. They only serve to influence the masses.
Important thing to note here is American presidential election is not a popularity contest. The winner doesn't neccesarily have to have more people voted for him. It is an electoral college contest. That's where Obama will hurt. He does not resonate with middle America. He insulted them by saying they cling to their guns and religions. These are who will decide the election. Obama had problem with this voting block during the primaries and I don't think he has improved anything.