Poll shows Obama is the worst president of the last 100 years, is that true or is it Carter or someone else?

I believe Obama is one of the worst presidents of all time but how bad will be determined by history. Right now, I feel Reagan and both Bushes are worse than Obama. However I am debating if Obama is worse than Carter and I waiting to see if Iran gets the bomb before 2012 or North Korea invades South Korea. If so, then I feel Obama will definitely be worse than Carter and probably will beat out Reagan as the worst president of all time.