Lower still, the Washington Post suggests, because the conservative base is abandoning him. (This, for a variety of reasons, isn't necessarily good news for those on the other side. The means to get them back could be very ugly. They aren't likely to support Democrats, etc.)
Bush won two presidential elections by pursuing a political and governing model that was predicated on winning and sustaining the loyal backing of social, economic and foreign policy conservatives. The strategy was based on the belief that conservatives, who are often more politically active than the general public, could be inspired to vote in larger numbers and would serve as a reliable foundation for his presidency. The theory, as explained by Bush strategists, is that the president would enjoy a floor below which his support would never fall.
It is now apparent that this floor has weakened dramatically -- and collapsed in places.