I see it as a manifestation of the primary season. The last poll by ARG was taken a month ago, just after the nomination fight got under way, and in that survey, he measured almost double at 34%. Now that the American public has had a good look at many "applicants" for his job, and seen the many qualities of the candidates on both sides of the aisle, there is a reminder that your president doesn't have to be irretrievably ignorant, record-breakingly arrogant, reflexively fascist, or hopelessly incompetent.
So much so, that by the time this poll came around again, and even Bush's most die-hard supporters had gotten a good look at the talents of Barack Obama, Hillary Clinton, John Edwards, John McCain and Mike Huckabee, half of them put up their hands and said "ok, ok, I was kidding before!"
